feat(highlight): warn when hunks exceed max_lines

Problem: when a hunk's highlighted lines exceed `max_lines`, syntax
highlighting is silently skipped. Users have no indication why parts
of their diff lack highlighting.

Solution: add `highlights.warn_max_lines` (default `true`) that emits
a `vim.notify` warning with the hunk index and line count vs threshold.
Also change `max_lines` to count only highlighted (`+`/`-`) lines
rather than total body lines including context.

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -68,10 +68,26 @@ body:
         load(vim.fn.system('curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua'))()
         require('lazy.nvim').setup({
           spec = {
-            'tpope/vim-fugitive',
+            { 'barrettruth/midnight.nvim', lazy = false, config = function() vim.cmd.colorscheme('midnight') end },
+            { 'tpope/vim-fugitive' },
+            { 'NeogitOrg/neogit', dependencies = { 'nvim-lua/plenary.nvim' } },
+            { 'lewis6991/gitsigns.nvim', config = true },
+            { 'rhysd/committia.vim' },
+            { 'nvim-telescope/telescope.nvim', dependencies = { 'nvim-lua/plenary.nvim' } },
             {
               'barrettruth/diffs.nvim',
-              opts = {},
+              init = function()
+                vim.g.diffs = {
+                  debug = '/tmp/diffs.log',
+                  integrations = {
+                    fugitive = true,
+                    neogit = true,
+                    gitsigns = true,
+                    committia = true,
+                    telescope = true,
+                  },
+                }
+              end,
             },
           },
         })

.github/workflows/quality.yaml

@@ -25,6 +25,7 @@ jobs:
               - '*.lua'
               - '.luarc.json'
               - '*.toml'
+              - 'vim.yaml'
             markdown:
               - '*.md'
 
@@ -35,11 +36,8 @@ jobs:
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
       - uses: actions/checkout@v4
-      - uses: JohnnyMorganz/stylua-action@v4
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-          version: 2.1.0
-          args: --check .
+      - uses: cachix/install-nix-action@v31
+      - run: nix develop --command stylua --check .
 
   lua-lint:
     name: Lua Lint Check
@@ -48,11 +46,8 @@ jobs:
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
       - uses: actions/checkout@v4
-      - name: Lint with Selene
-        uses: NTBBloodbath/selene-action@v1.0.0
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-          args: --display-style quiet .
+      - uses: cachix/install-nix-action@v31
+      - run: nix develop --command selene --display-style quiet .
 
   lua-typecheck:
     name: Lua Type Check
@@ -75,15 +70,5 @@ jobs:
     if: ${{ needs.changes.outputs.markdown == 'true' }}
     steps:
       - uses: actions/checkout@v4
-      - name: Setup pnpm
-        uses: pnpm/action-setup@v4
-        with:
-          version: 8
-      - name: Setup Node.js
-        uses: actions/setup-node@v4
-        with:
-          node-version: '20'
-      - name: Install prettier
-        run: pnpm add -g prettier@3.1.0
-      - name: Check markdown formatting with prettier
-        run: prettier --check .
+      - uses: cachix/install-nix-action@v31
+      - run: nix develop --command prettier --check .

.gitignore

@@ -5,4 +5,10 @@ doc/tags
 CLAUDE.md
 .claude/
 
+bench/
 node_modules/
+
+result
+result-*
+.direnv/
+.envrc

.luarc.json

@@ -1,8 +1,15 @@
 {
-  "runtime.version": "Lua 5.1",
+  "runtime.version": "LuaJIT",
   "runtime.path": ["lua/?.lua", "lua/?/init.lua"],
   "diagnostics.globals": ["vim", "jit"],
-  "workspace.library": ["$VIMRUNTIME/lua", "${3rd}/luv/library"],
+  "workspace.library": [
+    "$VIMRUNTIME/lua",
+    "${3rd}/luv/library",
+    "${3rd}/busted/library",
+    "${3rd}/luassert/library"
+  ],
   "workspace.checkThirdParty": false,
+  "diagnostics.libraryFiles": "Disable",
+  "workspace.ignoreDir": [".direnv"],
   "completion.callSnippet": "Replace"
 }

.styluaignore

@@ -0,0 +1 @@
+.direnv/

README.md

@@ -1,26 +1,25 @@
 # diffs.nvim
 
-**Syntax highlighting for diffs in Neovim**
+**Treesitter-powered Diff Syntax highlighting for Neovim**
 
-Enhance `vim-fugitive` and Neovim's built-in diff mode with language-aware
-syntax highlighting.
+Enhance Neovim's built-in diff mode (and much more!) with language-aware syntax
+highlighting driven by treesitter.
 
-![diffs.nvim preview](https://github.com/user-attachments/assets/d3d64c96-b824-4fcb-af7f-4aef3f7f498a)
+<video src="https://github.com/user-attachments/assets/24574916-ecb2-478e-a0ea-e4cdc971e310" width="100%" controls></video>
 
 ## Features
 
-- Treesitter syntax highlighting in `:Git` diffs and commit views
-- Diff header highlighting (`diff --git`, `index`, `---`, `+++`)
-- `:Gdiffsplit` / `:Gvdiffsplit` syntax through diff backgrounds
-- `:Gdiff` unified diff against any git revision with syntax highlighting
-- Fugitive status buffer keymaps (`du`/`dU`) for unified diffs
-- Background-only diff colors for any `&diff` buffer (`:diffthis`, `vimdiff`)
-- Vim syntax fallback for languages without a treesitter parser
-- Hunk header context highlighting (`@@ ... @@ function foo()`)
-- Character-level (intra-line) diff highlighting for changed characters
-- Inline merge conflict detection, highlighting, and resolution keymaps
-- Configurable debouncing, max lines, diff prefix concealment, blend alpha, and
-  highlight overrides
+- Treesitter syntax highlighting in vim-fugitive, Neogit, and `diff` filetype
+- Character-level intra-line diff highlighting (with optional
+  [vscode-diff](https://github.com/esmuellert/codediff.nvim) FFI backend for
+  word-level accuracy)
+- `:Gdiff` unified diff against any revision
+- Inline merge conflict detection, highlighting, and resolution
+- gitsigns.nvim blame popup highlighting
+- Email quoting/patch syntax support (`> diff ...`)
+- Vim syntax fallback
+- Configurable highlighiting blend & priorities
+- Context-inclusive, high-accuracy highlights
 
 ## Requirements
 
@@ -41,18 +40,59 @@ luarocks install diffs.nvim
 :help diffs.nvim
 ```
 
+## FAQ
+
+**Q: How do I install with lazy.nvim?**
+
+```lua
+{
+  'barrettruth/diffs.nvim',
+  init = function()
+    vim.g.diffs = {
+      ...
+    }
+  end,
+}
+```
+
+Do not lazy load `diffs.nvim` with `event`, `lazy`, `ft`, `config`, or `keys` to
+control loading - `diffs.nvim` lazy-loads itself.
+
+**Q: Does diffs.nvim support vim-fugitive/Neogit/gitsigns?**
+
+Yes. Enable integrations in your config:
+
+```lua
+vim.g.diffs = {
+  fugitive = true,
+  neogit = true,
+  gitsigns = true,
+}
+```
+
+See the documentation for more information.
+
 ## Known Limitations
 
 - **Incomplete syntax context**: Treesitter parses each diff hunk in isolation.
-  To improve accuracy, `diffs.nvim` reads lines from disk before and after each
-  hunk for parsing context (`highlights.context`, enabled by default with 25
-  lines). This resolves most boundary issues. Set
-  `highlights.context.enabled = false` to disable.
+  Context lines within the hunk provide syntactic context for the parser. In
+  rare cases, hunks that start or end mid-expression may produce imperfect
+  highlights due to treesitter error recovery.
 
-- **Syntax flashing**: `diffs.nvim` hooks into the `FileType fugitive` event
+- **Syntax "flashing"**: `diffs.nvim` hooks into the `FileType fugitive` event
   triggered by `vim-fugitive`, at which point the buffer is preliminarily
-  painted. The buffer is then re-painted after `debounce_ms` milliseconds,
-  causing an unavoidable visual "flash" even when `debounce_ms = 0`.
+  painted. The decoration provider applies highlights on the next redraw cycle,
+  causing a brief visual "flash".
+
+- **Cold Start**: Treesitter grammar loading (~10ms) and query compilation
+  (~4ms) are one-time costs per language per Neovim session. Each language pays
+  this cost on first encounter, which may cause a brief stutter when a diff
+  containing a new language first enters the viewport.
+
+- **Vim syntax fallback is deferred**: The vim syntax fallback (for languages
+  without a treesitter parser) cannot run inside the decoration provider's
+  redraw cycle due to Neovim's restriction on buffer mutations. Vim syntax
+  highlights for these hunks appear slightly delayed.
 
 - **Conflicting diff plugins**: `diffs.nvim` may not interact well with other
   plugins that modify diff highlighting. Known plugins that may conflict:
@@ -70,11 +110,16 @@ luarocks install diffs.nvim
 # Acknowledgements
 
 - [`vim-fugitive`](https://github.com/tpope/vim-fugitive)
-- [`codediff.nvim`](https://github.com/esmuellert/codediff.nvim)
+- [@esmuellert](https://github.com/esmuellert) /
+  [`codediff.nvim`](https://github.com/esmuellert/codediff.nvim) - vscode-diff
+  algorithm FFI backend for word-level intra-line accuracy
 - [`diffview.nvim`](https://github.com/sindrets/diffview.nvim)
 - [`difftastic`](https://github.com/Wilfred/difftastic)
 - [`mini.diff`](https://github.com/echasnovski/mini.diff)
 - [`gitsigns.nvim`](https://github.com/lewis6991/gitsigns.nvim)
 - [`git-conflict.nvim`](https://github.com/akinsho/git-conflict.nvim)
 - [@phanen](https://github.com/phanen) - diff header highlighting, unknown
-  filetype fix, shebang/modeline detection, treesitter injection support
+  filetype fix, shebang/modeline detection, treesitter injection support,
+  decoration provider highlighting architecture, gitsigns blame popup
+  highlighting
+- [@tris203](https://github.com/tris203) - support for transparent backgrounds

doc/diffs.nvim.txt

@@ -6,44 +6,72 @@ License: MIT
 ==============================================================================
 INTRODUCTION                                                       *diffs.nvim*
 
-diffs.nvim adds syntax highlighting to diff views. It overlays language-aware
-highlights on top of default diff highlighting in vim-fugitive and Neovim's
-built-in diff mode.
+diffs.nvim adds language-aware syntax highlighting to unified diff content
+in Neovim buffers. It replaces flat `diffAdded`/`diffRemoved` coloring with
+treesitter syntax, blended line backgrounds, and character-level intra-line
+diffs.
+
+With no configuration, diffs.nvim provides:
+- `gitcommit` diff highlighting (e.g., `git commit --verbose`)
+- Inline merge conflict detection, highlighting, and resolution
+- Background-only diff colors for `&diff` buffers (vimdiff, diffthis)
+
+All other integrations are opt-in. See |diffs-integrations|.
 
 Features: ~
-- Syntax highlighting in |:Git| summary diffs and commit detail views
-- Diff header highlighting (`diff --git`, `index`, `---`, `+++`)
-- Syntax highlighting in |:Gdiffsplit| / |:Gvdiffsplit| side-by-side diffs
-- |:Gdiff| command for unified diff against any git revision
-- Background-only diff colors for any `&diff` buffer (vimdiff, diffthis, etc.)
+- Treesitter syntax highlighting in diff hunks
+- Character-level intra-line diff highlighting
 - Vim syntax fallback for languages without a treesitter parser
 - Blended diff background colors that preserve syntax visibility
 - Optional diff prefix (`+`/`-`/` `) concealment
 - Gutter (line number) highlighting
-- Inline merge conflict marker detection, highlighting, and resolution
+- |:Gdiff| unified diff against any revision
+- Email quoting/patch syntax support (`> diff ...`)
+
+==============================================================================
+CONTENTS                                                      *diffs-contents*
+
+  1. Introduction ............................................... |diffs.nvim|
+  2. Requirements ....................................... |diffs-requirements|
+  3. Setup ..................................................... |diffs-setup|
+  4. Configuration ............................................ |diffs-config|
+  5. Commands ............................................... |diffs-commands|
+  6. Mappings ............................................... |diffs-mappings|
+  7. Integrations ..................................... |diffs-integrations|
+       Fugitive .......................................... |diffs-fugitive|
+       Neogit .............................................. |diffs-neogit|
+       Gitsigns .......................................... |diffs-gitsigns|
+       Telescope ........................................ |diffs-telescope|
+  8. Conflict Resolution .................................... |diffs-conflict|
+  9. Merge Diff Resolution ..................................... |diffs-merge|
+ 10. API ......................................................... |diffs-api|
+ 11. Implementation ................................... |diffs-implementation|
+ 12. Known Limitations ................................... |diffs-limitations|
+ 13. Highlight Groups ..................................... |diffs-highlights|
+ 14. Health Check ............................................. |diffs-health|
+ 15. Acknowledgements ............................... |diffs-acknowledgements|
 
 ==============================================================================
 REQUIREMENTS                                              *diffs-requirements*
 
 - Neovim 0.9.0+
-- vim-fugitive (https://github.com/tpope/vim-fugitive) (optional, for unified
-  diff syntax highlighting in |:Git| and commit views)
 - Treesitter parsers for languages you want highlighted
 
-Note: The diff mode feature (background-only colors for |:diffthis|, vimdiff,
-etc.) works without vim-fugitive.
-
 ==============================================================================
 SETUP                                                            *diffs-setup*
 
-Using lazy.nvim: >lua
-    {
-      'barrettruth/diffs.nvim',
-      dependencies = { 'tpope/vim-fugitive' },
-    }
+Install with lazy.nvim: >lua
+    { 'barrettruth/diffs.nvim' }
 <
-The plugin works automatically with no configuration required. For
-customization, see |diffs-config|.
+
+Do not lazy load with `event`, `lazy`, `ft`, `config`, or `keys` —
+diffs.nvim lazy-loads itself.
+
+NOTE: Load your colorscheme before diffs.nvim. With lazy.nvim, set
+`priority = 1000` and `lazy = false` on your colorscheme plugin.
+
+See |diffs-config| for customization, |diffs-integrations| for plugin
+support.
 
 ==============================================================================
 CONFIGURATION                                                   *diffs-config*
@@ -52,12 +80,20 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
 >lua
     vim.g.diffs = {
       debug = false,
-      debounce_ms = 0,
       hide_prefix = false,
+      integrations = {
+        fugitive = false,
+        neogit = false,
+        gitsigns = false,
+        committia = false,
+        telescope = false,
+      },
+      extra_filetypes = {},
       highlights = {
         background = true,
         gutter = true,
         blend_alpha = 0.6,
+        warn_max_lines = true,
         context = {
           enabled = true,
           lines = 25,
@@ -67,7 +103,7 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
           max_lines = 500,
         },
         vim = {
-          enabled = false,
+          enabled = true,
           max_lines = 200,
         },
         intra = {
@@ -75,23 +111,26 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
           algorithm = 'default',
           max_lines = 500,
         },
+        priorities = {
+          clear = 198,
+          syntax = 199,
+          line_bg = 200,
+          char_bg = 201,
+        },
         overrides = {},
       },
-      fugitive = {
-        horizontal = 'du',
-        vertical = 'dU',
-      },
       conflict = {
         enabled = true,
         disable_diagnostics = true,
         show_virtual_text = true,
+        show_actions = false,
         keymaps = {
           ours = 'doo',
           theirs = 'dot',
           both = 'dob',
           none = 'don',
-          next = ']x',
-          prev = '[x',
+          next = ']c',
+          prev = '[c',
         },
       },
     }
@@ -102,11 +141,6 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              Enable debug logging to |:messages| with
                              `[diffs]` prefix.
 
-        {debounce_ms}        (integer, default: 0)
-                             Debounce delay in milliseconds for re-highlighting
-                             after buffer changes. Lower values feel snappier
-                             but use more CPU.
-
         {hide_prefix}        (boolean, default: false)
                              Hide diff prefixes (`+`/`-`/` `) using virtual
                              text overlay. Makes code appear without the
@@ -114,14 +148,84 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              is also enabled, the overlay inherits the line's
                              background color.
 
+        {integrations}       (table, default: all false)
+                             Integration toggles. Each key accepts `true`,
+                             `false`, or a table with sub-options. Passing
+                             `true` or a table enables the integration;
+                             `false` disables it. See |diffs-integrations|.
+                                                   *diffs.IntegrationsConfig*
+                             Fields: ~
+
+            {fugitive}       (boolean|table, default: false)
+                             Enable vim-fugitive integration. Pass `true`
+                             for defaults, or a table with sub-options
+                             (see |diffs.FugitiveConfig|). When active,
+                             the `fugitive` filetype is registered and
+                             status buffer keymaps are set. >lua
+                                 vim.g.diffs = {
+                                   integrations = { fugitive = true },
+                                 }
+                                 vim.g.diffs = {
+                                   integrations = {
+                                     fugitive = { horizontal = 'dd' },
+                                   },
+                                 }
+<
+
+            {neogit}         (boolean|table, default: false)
+                             Enable Neogit integration. When active,
+                             `NeogitStatus`, `NeogitCommitView`, and
+                             `NeogitDiffView` filetypes are registered.
+                             See |diffs-neogit|. >lua
+                                 integrations = { neogit = true }
+<
+
+            {gitsigns}       (boolean|table, default: false)
+                             Enable gitsigns.nvim blame popup highlighting.
+                             See |diffs-gitsigns|. >lua
+                                 integrations = { gitsigns = true }
+<
+
+            {committia}      (boolean|table, default: false)
+                             Enable committia.vim integration. When active,
+                             committia's diff pane receives treesitter
+                             syntax and intra-line diffs. >lua
+                                 integrations = { committia = true }
+<
+
+            {telescope}      (boolean|table, default: false)
+                             Enable telescope.nvim preview highlighting.
+                             See |diffs-telescope|. >lua
+                                 integrations = { telescope = true }
+<
+
+                             Legacy top-level keys (`vim.g.diffs.fugitive`,
+                             etc.) still work but emit a deprecation
+                             warning. If both `integrations` and top-level
+                             keys are present, `integrations` wins and
+                             the stale keys are ignored with a warning.
+
+        {extra_filetypes}    (table, default: {})
+                             Additional filetypes to attach to, beyond the
+                             built-in `git`, `gitcommit`, and any enabled
+                             integration filetypes. Use this to enable
+                             highlighting in plain `.diff` / `.patch`
+                             files: >lua
+                                 vim.g.diffs = {
+                                   extra_filetypes = { 'diff' },
+                                 }
+<
+                             Adding `'diff'` also enables highlighting in
+                             picker preview buffers that set `filetype=diff`:
+                             telescope.nvim (git_commits, git_bcommits,
+                             git_status), snacks.nvim (syntax style only),
+                             and fzf-lua (builtin previewer only). Terminal-
+                             based previewers are not supported.
+
         {highlights}         (table, default: see below)
                              Controls which highlight features are enabled.
                              See |diffs.Highlights| for fields.
 
-        {fugitive}           (table, default: see below)
-                             Fugitive status buffer keymap options.
-                             See |diffs.FugitiveConfig| for fields.
-
         {conflict}           (table, default: see below)
                              Inline merge conflict resolution options.
                              See |diffs.ConflictConfig| for fields.
@@ -138,11 +242,21 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              Only visible if line numbers are enabled.
 
         {blend_alpha}        (number, default: 0.6)
-                             Alpha value for character-level blend intensity.
-                             Controls how strongly changed characters stand
-                             out from the line-level background. Must be
-                             between 0 and 1 (inclusive). Higher values
-                             produce more vivid character-level highlights.
+                             Alpha value for diff line background intensity.
+                             Controls how strongly diff lines (adds/deletes)
+                             stand out from the editor background. Intra-line
+                             highlights use alpha + 0.3 (capped at 1.0) for
+                             extra contrast. Must be between 0 and 1
+                             (inclusive). Higher values produce more vivid
+                             backgrounds.
+
+        {warn_max_lines}     (boolean, default: true)
+                             Show a |vim.notify()| warning when a hunk's
+                             highlighted lines (`+`/`-`) exceed {max_lines}
+                             and syntax highlighting is skipped. The warning
+                             includes the 1-indexed hunk number and the
+                             line count vs. threshold so the user knows
+                             which hunk was affected and what to adjust.
 
         {context}            (table, default: see below)
                              Syntax parsing context options.
@@ -153,13 +267,17 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              See |diffs.TreesitterConfig| for fields.
 
         {vim}                (table, default: see below)
-                             Vim syntax highlighting options (experimental).
+                             Vim syntax fallback highlighting options.
                              See |diffs.VimConfig| for fields.
 
         {intra}              (table, default: see below)
                              Character-level (intra-line) diff highlighting.
                              See |diffs.IntraConfig| for fields.
 
+        {priorities}         (table, default: see below)
+                             Extmark priority values.
+                             See |diffs.PrioritiesConfig| for fields.
+
         {overrides}          (table, default: {})
                              Map of highlight group names to highlight
                              definitions (see |nvim_set_hl()|). Applied
@@ -170,16 +288,42 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                                                       *diffs.ContextConfig*
     Context config fields: ~
         {enabled}            (boolean, default: true)
-                             Read lines from disk before and after each hunk
-                             to provide surrounding syntax context. Improves
-                             accuracy at hunk boundaries where incomplete
-                             constructs (e.g., a function definition with no
-                             body) would otherwise confuse the parser.
+                             Read surrounding code from the working tree
+                             file and feed it into the treesitter string
+                             parser. Uses the hunk's `@@ +start,count @@`
+                             line numbers to read lines before and after
+                             the hunk from disk. Improves syntax accuracy
+                             when the hunk is inside an incomplete construct
+                             (e.g., a table literal or function body whose
+                             opening is not visible in the hunk's own
+                             context lines).
 
         {lines}              (integer, default: 25)
-                             Number of context lines to read in each
-                             direction. Lines are read with early exit —
-                             cost scales with this value, not file size.
+                             Max context lines to read in each direction.
+                             Files are read once per parse and cached across
+                             hunks in the same file.
+
+                                                   *diffs.PrioritiesConfig*
+    Priorities config fields: ~
+        {clear}              (integer, default: 198)
+                             Priority for `DiffsClear` extmarks that reset
+                             underlying diff foreground colors. Must be
+                             below {syntax}.
+
+        {syntax}             (integer, default: 199)
+                             Priority for treesitter and vim syntax extmarks.
+                             Must be below {line_bg} so that colorscheme
+                             backgrounds on syntax groups do not obscure
+                             line-level diff backgrounds.
+
+        {line_bg}            (integer, default: 200)
+                             Priority for `DiffsAdd`/`DiffsDelete` line
+                             background extmarks. Must be below {char_bg}.
+
+        {char_bg}            (integer, default: 201)
+                             Priority for `DiffsAddText`/`DiffsDeleteText`
+                             character-level background extmarks. Highest
+                             priority so changed characters stand out.
 
                                                     *diffs.TreesitterConfig*
     Treesitter config fields: ~
@@ -187,23 +331,29 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              Apply treesitter syntax highlighting to code.
 
         {max_lines}          (integer, default: 500)
-                             Skip treesitter highlighting for hunks larger than
-                             this many lines. Prevents lag on massive diffs.
+                             Skip treesitter highlighting for hunks with more
+                             highlighted lines (`+`/`-`) than this threshold.
+                             Context lines are not counted. Prevents lag on
+                             massive diffs.
 
                                                           *diffs.VimConfig*
     Vim config fields: ~
-        {enabled}            (boolean, default: false)
+        {enabled}            (boolean, default: true)
                              Use vim syntax highlighting as fallback when no
                              treesitter parser is available for a language.
                              Creates a scratch buffer, sets the filetype, and
                              queries |synID()| per character to extract
-                             highlight groups. Slower than treesitter but
-                             covers languages without a TS parser installed.
+                             highlight groups. Deferred via |vim.schedule()|
+                             so it never blocks the first paint. Slower than
+                             treesitter but covers languages without a TS
+                             parser installed (e.g., COBOL, Fortran).
 
         {max_lines}          (integer, default: 200)
-                             Skip vim syntax highlighting for hunks larger than
-                             this many lines. Lower than the treesitter default
-                             due to the per-character cost of |synID()|.
+                             Skip vim syntax highlighting for hunks with more
+                             highlighted lines (`+`/`-`) than this threshold.
+                             Context lines are not counted. Lower than the
+                             treesitter default due to the per-character cost
+                             of |synID()|.
 
                                                         *diffs.IntraConfig*
     Intra config fields: ~
@@ -222,8 +372,9 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              (falls back to default if not available).
 
         {max_lines}          (integer, default: 500)
-                             Skip character-level highlighting for hunks larger
-                             than this many lines.
+                             Skip character-level highlighting for hunks with
+                             more highlighted lines (`+`/`-`) than this
+                             threshold. Context lines are not counted.
 
     Note: Header context (e.g., `@@ -10,3 +10,4 @@ func()`) is always
     highlighted with treesitter when a parser is available.
@@ -280,6 +431,67 @@ Example configuration: >lua
     vim.keymap.set('n', '<leader>gD', '<Plug>(diffs-gvdiff)')
 <
 
+                                              *<Plug>(diffs-conflict-ours)*
+<Plug>(diffs-conflict-ours)
+                        Accept current (ours) change. Replaces the
+                        conflict block with ours content.
+
+                                            *<Plug>(diffs-conflict-theirs)*
+<Plug>(diffs-conflict-theirs)
+                        Accept incoming (theirs) change. Replaces the
+                        conflict block with theirs content.
+
+                                              *<Plug>(diffs-conflict-both)*
+<Plug>(diffs-conflict-both)
+                        Accept both changes (ours then theirs).
+
+                                              *<Plug>(diffs-conflict-none)*
+<Plug>(diffs-conflict-none)
+                        Reject both changes (delete entire block).
+
+                                              *<Plug>(diffs-conflict-next)*
+<Plug>(diffs-conflict-next)
+                        Jump to next conflict marker. Wraps around.
+
+                                              *<Plug>(diffs-conflict-prev)*
+<Plug>(diffs-conflict-prev)
+                        Jump to previous conflict marker. Wraps around.
+
+Example configuration: >lua
+    vim.keymap.set('n', 'co', '<Plug>(diffs-conflict-ours)')
+    vim.keymap.set('n', 'ct', '<Plug>(diffs-conflict-theirs)')
+    vim.keymap.set('n', 'cb', '<Plug>(diffs-conflict-both)')
+    vim.keymap.set('n', 'cn', '<Plug>(diffs-conflict-none)')
+    vim.keymap.set('n', ']c', '<Plug>(diffs-conflict-next)')
+    vim.keymap.set('n', '[c', '<Plug>(diffs-conflict-prev)')
+<
+
+                                                 *<Plug>(diffs-merge-ours)*
+<Plug>(diffs-merge-ours)
+                        Accept ours in a merge diff view. Resolves the
+                        conflict in the working file with ours content.
+
+                                               *<Plug>(diffs-merge-theirs)*
+<Plug>(diffs-merge-theirs)
+                        Accept theirs in a merge diff view.
+
+                                                 *<Plug>(diffs-merge-both)*
+<Plug>(diffs-merge-both)
+                        Accept both (ours then theirs) in a merge diff view.
+
+                                                 *<Plug>(diffs-merge-none)*
+<Plug>(diffs-merge-none)
+                        Reject both in a merge diff view.
+
+                                                 *<Plug>(diffs-merge-next)*
+<Plug>(diffs-merge-next)
+                        Jump to next unresolved conflict hunk in merge diff.
+
+                                                 *<Plug>(diffs-merge-prev)*
+<Plug>(diffs-merge-prev)
+                        Jump to previous unresolved conflict hunk in merge
+                        diff.
+
 Diff buffer mappings: ~
                                                               *diffs-q*
     q               Close the diff window. Available in all `diffs://`
@@ -287,10 +499,46 @@ Diff buffer mappings: ~
                     or the fugitive status keymaps.
 
 ==============================================================================
-FUGITIVE STATUS KEYMAPS                                   *diffs-fugitive*
+INTEGRATIONS                                           *diffs-integrations*
 
-When inside a vim-fugitive |:Git| status buffer, diffs.nvim provides keymaps
-to open unified diffs for files or entire sections.
+diffs.nvim integrates with several plugins. There are two attachment
+patterns:
+
+Automatic: ~
+Enable via config toggles. The plugin registers `FileType` autocmds for
+each integration's filetypes and attaches automatically.
+>lua
+    vim.g.diffs = {
+      integrations = {
+        fugitive = true,
+        neogit = true,
+        gitsigns = true,
+      },
+    }
+<
+
+Opt-in: ~
+For filetypes not covered by a built-in integration, use `extra_filetypes`
+to attach to any buffer whose content looks like a diff.
+>lua
+    vim.g.diffs = { extra_filetypes = { 'diff' } }
+<
+
+------------------------------------------------------------------------------
+FUGITIVE                                                      *diffs-fugitive*
+
+Enable vim-fugitive (https://github.com/tpope/vim-fugitive) support: >lua
+    vim.g.diffs = { integrations = { fugitive = true } }
+<
+
+|:Git| status and commit views receive treesitter syntax, line backgrounds,
+and intra-line diffs. |:Gdiff| opens a unified diff against any revision
+(see |diffs-commands|).
+
+Fugitive status keymaps: ~
+
+When inside a |:Git| status buffer, diffs.nvim provides keymaps to open
+unified diffs for files or entire sections.
 
 Keymaps: ~
                                                           *diffs-du* *diffs-dU*
@@ -310,6 +558,7 @@ Behavior by file status: ~
     A           Staged      (empty)         index           file as all-added
     D           Staged      HEAD            (empty)         file as all-removed
     R           Staged      HEAD:oldname    index:newname   content diff
+    U           Unstaged    :2: (ours)      :3: (theirs)    merge diff
     ?           Untracked   (empty)         working tree    file as all-added
 
 On section headers, the keymap runs `git diff` (or `git diff --cached` for
@@ -320,12 +569,17 @@ Configuration: ~
                                                       *diffs.FugitiveConfig*
 >lua
     vim.g.diffs = {
-      fugitive = {
-        horizontal = 'du',  -- keymap for horizontal split, false to disable
-        vertical = 'dU',    -- keymap for vertical split, false to disable
+      integrations = {
+        fugitive = {
+          horizontal = 'du',  -- keymap for horizontal split, false to disable
+          vertical = 'dU',    -- keymap for vertical split, false to disable
+        },
       },
     }
 <
+    Passing a table enables fugitive integration. Use `fugitive = false`
+    to disable. There is no `enabled` field; table presence is sufficient.
+
     Fields: ~
         {horizontal}         (string|false, default: 'du')
                              Keymap for unified diff in horizontal split.
@@ -335,6 +589,53 @@ Configuration: ~
                              Keymap for unified diff in vertical split.
                              Set to `false` to disable.
 
+------------------------------------------------------------------------------
+NEOGIT                                                          *diffs-neogit*
+
+Enable Neogit (https://github.com/NeogitOrg/neogit) support: >lua
+    vim.g.diffs = { integrations = { neogit = true } }
+<
+
+Expanding a diff in a Neogit buffer (e.g., TAB on a file in the status
+view) applies treesitter syntax highlighting and intra-line diffs to the
+hunk lines.
+
+------------------------------------------------------------------------------
+GITSIGNS                                                      *diffs-gitsigns*
+
+Enable gitsigns.nvim (https://github.com/lewis6991/gitsigns.nvim) blame
+popup highlighting: >lua
+    vim.g.diffs = { integrations = { gitsigns = true } }
+<
+
+`:Gitsigns blame_line full=true` popups receive treesitter syntax, line
+backgrounds, and intra-line diffs.
+
+Highlights are applied in a separate `diffs-gitsigns` namespace and do not
+interfere with the main decoration provider used for diff buffers.
+
+------------------------------------------------------------------------------
+TELESCOPE                                                  *diffs-telescope*
+
+Enable telescope.nvim (https://github.com/nvim-telescope/telescope.nvim)
+preview highlighting: >lua
+    vim.g.diffs = { integrations = { telescope = true } }
+<
+
+Telescope does not set `filetype=diff` on preview buffers — it calls
+`vim.treesitter.start(bufnr, "diff")` directly, so diffs.nvim's `FileType`
+autocmd never fires. This integration listens for the
+`User TelescopePreviewerLoaded` event and attaches to the preview buffer.
+
+Pickers that show diff content (e.g. `git_bcommits`, `git_status`) will
+receive treesitter syntax, line backgrounds, and intra-line diffs in the
+preview pane.
+
+Known issue: Telescope's previewer may render the first line of the preview
+buffer with a black background regardless of colorscheme. This is a
+Telescope artifact unrelated to diffs.nvim. Tracked upstream:
+https://github.com/nvim-telescope/telescope.nvim/issues/3626
+
 ==============================================================================
 CONFLICT RESOLUTION                                          *diffs-conflict*
 
@@ -354,13 +655,15 @@ Configuration: ~
         enabled = true,
         disable_diagnostics = true,
         show_virtual_text = true,
+        show_actions = false,
+        priority = 200,
         keymaps = {
           ours = 'doo',
           theirs = 'dot',
           both = 'dob',
           none = 'don',
-          next = ']x',
-          prev = '[x',
+          next = ']c',
+          prev = '[c',
         },
       },
     }
@@ -380,9 +683,37 @@ Configuration: ~
                              diagnostics alone.
 
         {show_virtual_text}  (boolean, default: true)
-                             Show virtual text labels (" current" and
-                             " incoming") at the end of `<<<<<<<` and
-                             `>>>>>>>` marker lines.
+                             Show `(current)` and `(incoming)` labels at
+                             the end of `<<<<<<<` and `>>>>>>>` marker
+                             lines. Also controls hunk hints in merge
+                             diff views.
+
+        {format_virtual_text} (function|nil, default: nil)
+                             Custom formatter for virtual text labels.
+                             Receives `(side, keymap)` where `side` is
+                             `"ours"` or `"theirs"` and `keymap` is the
+                             configured keymap string or `false`. Return
+                             a string (label text without parens) or
+                             `nil` to hide the label. Example: >lua
+                                 format_virtual_text = function(side, keymap)
+                                   if keymap then
+                                     return side .. ' [' .. keymap .. ']'
+                                   end
+                                   return side
+                                 end
+<
+
+        {show_actions}       (boolean, default: false)
+                             Show a codelens-style action line above each
+                             `<<<<<<<` marker listing available resolution
+                             keymaps. Renders as virtual lines using the
+                             `DiffsConflictActions` highlight group.
+                             Only keymaps that are not `false` appear.
+
+        {priority}           (integer, default: 200)
+                             Extmark priority for conflict region
+                             backgrounds and markers. Adjust if other
+                             plugins use the same priority range.
 
         {keymaps}            (table, default: see above)
                              Buffer-local keymaps for conflict resolution
@@ -403,10 +734,10 @@ Configuration: ~
         {none}               (string|false, default: 'don')
                              Reject both changes (delete entire block).
 
-        {next}               (string|false, default: ']x')
+        {next}               (string|false, default: ']c')
                              Jump to next conflict marker. Wraps around.
 
-        {prev}               (string|false, default: '[x')
+        {prev}               (string|false, default: '[c')
                              Jump to previous conflict marker. Wraps
                              around.
 
@@ -423,6 +754,31 @@ User events: ~
                                 })
 <
 
+==============================================================================
+MERGE DIFF RESOLUTION                                       *diffs-merge*
+
+When pressing `du`/`dU` on an unmerged (`U`) file in the fugitive status
+buffer, diffs.nvim opens a unified diff of ours (`git show :2:path`) vs
+theirs (`git show :3:path`) with full treesitter and intra-line highlighting.
+
+The same conflict resolution keymaps (`doo`/`dot`/`dob`/`don`/`]c`/`[c`)
+are available on the diff buffer. They resolve conflicts in the working
+file by matching diff hunks to conflict markers:
+
+- `doo` replaces the conflict region with ours content
+- `dot` replaces the conflict region with theirs content
+- `dob` replaces with both (ours then theirs)
+- `don` removes the conflict region entirely
+- `]c`/`[c` navigate between unresolved conflict hunks
+
+Resolved hunks are marked with `(resolved)` virtual text. Hunks that
+correspond to auto-merged content (no conflict markers) show an
+informational notification and are left unchanged.
+
+The working file buffer is modified in place; save it when ready.
+Phase 1 inline conflict highlights (see |diffs-conflict|) are refreshed
+automatically after each resolution.
+
 ==============================================================================
 API                                                                *diffs-api*
 
@@ -444,8 +800,8 @@ refresh({bufnr})                                           *diffs.refresh()*
 IMPLEMENTATION                                        *diffs-implementation*
 
 Summary / commit detail views: ~
-1. `FileType fugitive` or `FileType git` (for `fugitive://` buffers)
-   triggers |diffs.attach()|
+1. `FileType` autocmd for computed filetypes (see |diffs-config|) triggers
+   |diffs.attach()|. For `git` buffers, only `fugitive://` URIs are attached.
 2. The buffer is parsed to detect file headers (`M path/to/file`,
    `diff --git a/... b/...`) and hunk headers (`@@ -10,3 +10,4 @@`)
 3. For each hunk:
@@ -454,13 +810,14 @@ Summary / commit detail views: ~
    - Code is parsed with |vim.treesitter.get_string_parser()|
    - If no treesitter parser and `vim.enabled`: vim syntax fallback via
      scratch buffer and |synID()|
-   - `Normal` extmarks at priority 198 clear underlying diff foreground
-   - Background extmarks (`DiffsAdd`/`DiffsDelete`) at priority 199
-   - Syntax highlights are applied as extmarks at priority 200
+   - `DiffsClear` extmarks at priority 198 clear underlying diff foreground
+   - Syntax highlights are applied as extmarks at priority 199
+   - Background extmarks (`DiffsAdd`/`DiffsDelete`) at priority 200
    - Character-level diff extmarks (`DiffsAddText`/`DiffsDeleteText`) at
      priority 201 overlay changed characters with an intense background
    - Conceal extmarks hide diff prefixes when `hide_prefix` is enabled
-4. Re-highlighting occurs on `TextChanged` (debounced) and `Syntax` events
+   - All priorities are configurable via |diffs.PrioritiesConfig|
+4. A decoration provider re-highlights visible hunks on each redraw
 
 Diff mode views: ~
 1. `OptionSet diff` detects when any window enters diff mode
@@ -474,15 +831,14 @@ KNOWN LIMITATIONS                                       *diffs-limitations*
 
 Incomplete Syntax Context ~
                                                       *diffs-syntax-context*
-Treesitter parses each diff hunk in isolation. To provide surrounding code
-context, diffs.nvim reads lines from disk before and after each hunk
-(see |diffs.ContextConfig|, enabled by default). This resolves most boundary
-issues where incomplete constructs (e.g., a function definition at the edge
-of a hunk with no body) would confuse the parser.
-
-Set `highlights.context.enabled = false` to disable context padding. In rare
-cases, context padding may not help if the relevant surrounding code is very
-far from the hunk boundaries.
+Treesitter parses each diff hunk in isolation. When `highlights.context` is
+enabled (the default), surrounding code is read from the working tree file
+and fed into the parser to improve accuracy at hunk boundaries. This helps
+when a hunk is inside a table, function body, or loop whose opening is
+beyond the hunk's own context lines. Requires `repo_root` and
+`file_new_start` to be available on the hunk (true for standard unified
+diffs). In rare cases, hunks that start or end mid-expression may still
+produce imperfect highlights due to treesitter error recovery.
 
 Syntax Highlighting Flash ~
                                                              *diffs-flash*
@@ -491,14 +847,8 @@ the buffer briefly shows fugitive's default diff highlighting before
 diffs.nvim applies treesitter highlights.
 
 This occurs because diffs.nvim hooks into the `FileType fugitive` event,
-which fires after vim-fugitive has already painted the buffer. Even with
-`debounce_ms = 0`, the re-painting goes through Neovim's event loop.
-
-To minimize the flash, use a low debounce value: >lua
-    vim.g.diffs = {
-      debounce_ms = 0,
-    }
-<
+which fires after vim-fugitive has already painted the buffer. The
+decoration provider applies highlights on the next redraw cycle.
 
 Conflicting Diff Plugins ~
                                                     *diffs-plugin-conflicts*
@@ -540,6 +890,7 @@ character-level groups blend at 60% for more contrast. Line-number groups
 combine both: background from the line-level blend, foreground from the
 character-level blend.
 
+
 Fugitive unified diff highlights: ~
                                                                   *DiffsAdd*
     DiffsAdd            Background for `+` lines. Derived by blending
@@ -600,6 +951,10 @@ Conflict highlights: ~
                                                       *DiffsConflictBaseNr*
     DiffsConflictBaseNr Line number for base content lines (diff3).
 
+                                                    *DiffsConflictActions*
+    DiffsConflictActions Dimmed foreground (no bold) for the codelens-style
+                        action line shown when `show_actions` is true.
+
 Diff mode window highlights: ~
 These are used for |winhighlight| remapping in `&diff` windows.
 
@@ -652,7 +1007,9 @@ ACKNOWLEDGEMENTS                                     *diffs-acknowledgements*
 - codediff.nvim (https://github.com/esmuellert/codediff.nvim)
 - diffview.nvim (https://github.com/sindrets/diffview.nvim)
 - @phanen (https://github.com/phanen) - diff header highlighting,
-  treesitter injection support
+  treesitter injection support, blame_hl.nvim (gitsigns blame popup
+  highlighting inspiration)
+- @tris203 (https://github.com/tris203) - support for transparent backgrounds
 
 ==============================================================================
  vim:tw=78:ts=8:ft=help:norl:

flake.lock

@@ -0,0 +1,43 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1770812194,
+        "narHash": "sha256-OH+lkaIKAvPXR3nITO7iYZwew2nW9Y7Xxq0yfM/UcUU=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "8482c7ded03bae7550f3d69884f1e611e3bd19e8",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs",
+        "systems": "systems"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,53 @@
+{
+  description = "diffs.nvim — syntax highlighting for diffs in Neovim";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    systems.url = "github:nix-systems/default";
+  };
+
+  outputs =
+    {
+      nixpkgs,
+      systems,
+      ...
+    }:
+    let
+      forEachSystem =
+        f: nixpkgs.lib.genAttrs (import systems) (system: f nixpkgs.legacyPackages.${system});
+    in
+    {
+      formatter = forEachSystem (pkgs: pkgs.nixfmt-tree);
+
+      devShells = forEachSystem (pkgs: {
+        default =
+          let
+            ts-plugin = pkgs.vimPlugins.nvim-treesitter.withPlugins (p: [ p.diff ]);
+            diff-grammar = pkgs.vimPlugins.nvim-treesitter-parsers.diff;
+            luaEnv = pkgs.luajit.withPackages (
+              ps: with ps; [
+                busted
+                nlua
+              ]
+            );
+            busted-with-grammar = pkgs.writeShellScriptBin "busted" ''
+              nvim_bin=$(which nvim)
+              tmpdir=$(mktemp -d)
+              trap 'rm -rf "$tmpdir"' EXIT
+              printf '#!/bin/sh\nexec "%s" --cmd "set rtp+=${ts-plugin}/runtime" --cmd "set rtp+=${diff-grammar}" "$@"\n' "$nvim_bin" > "$tmpdir/nvim"
+              chmod +x "$tmpdir/nvim"
+              PATH="$tmpdir:$PATH" exec ${luaEnv}/bin/busted "$@"
+            '';
+          in
+          pkgs.mkShell {
+            packages = [
+              busted-with-grammar
+              pkgs.prettier
+              pkgs.stylua
+              pkgs.selene
+              pkgs.lua-language-server
+            ];
+          };
+      });
+    };
+}

lua/diffs/commands.lua

@@ -36,6 +36,24 @@ function M.find_hunk_line(diff_lines, hunk_position)
   return nil
 end
 
+---@param lines string[]
+---@return string[]
+function M.filter_combined_diffs(lines)
+  local result = {}
+  local skip = false
+  for _, line in ipairs(lines) do
+    if line:match('^diff %-%-cc ') then
+      skip = true
+    elseif line:match('^diff %-%-git ') then
+      skip = false
+    end
+    if not skip then
+      table.insert(result, line)
+    end
+  end
+  return result
+end
+
 ---@param old_lines string[]
 ---@param new_lines string[]
 ---@param old_name string
@@ -69,6 +87,33 @@ local function generate_unified_diff(old_lines, new_lines, old_name, new_name)
   return result
 end
 
+---@param raw_lines string[]
+---@param repo_root string
+---@return string[]
+local function replace_combined_diffs(raw_lines, repo_root)
+  local unmerged_files = {}
+  for _, line in ipairs(raw_lines) do
+    local cc_file = line:match('^diff %-%-cc (.+)$')
+    if cc_file then
+      table.insert(unmerged_files, cc_file)
+    end
+  end
+
+  local result = M.filter_combined_diffs(raw_lines)
+
+  for _, filename in ipairs(unmerged_files) do
+    local filepath = repo_root .. '/' .. filename
+    local old_lines = git.get_file_content(':2', filepath) or {}
+    local new_lines = git.get_file_content(':3', filepath) or {}
+    local diff_lines = generate_unified_diff(old_lines, new_lines, filename, filename)
+    for _, dl in ipairs(diff_lines) do
+      table.insert(result, dl)
+    end
+  end
+
+  return result
+end
+
 ---@param revision? string
 ---@param vertical? boolean
 function M.gdiff(revision, vertical)
@@ -138,6 +183,7 @@ end
 ---@field vertical? boolean
 ---@field staged? boolean
 ---@field untracked? boolean
+---@field unmerged? boolean
 ---@field old_filepath? string
 ---@field hunk_position? { hunk_header: string, offset: integer }
 
@@ -157,7 +203,17 @@ function M.gdiff_file(filepath, opts)
   local old_lines, new_lines, err
   local diff_label
 
-  if opts.untracked then
+  if opts.unmerged then
+    old_lines = git.get_file_content(':2', filepath)
+    if not old_lines then
+      old_lines = {}
+    end
+    new_lines = git.get_file_content(':3', filepath)
+    if not new_lines then
+      new_lines = {}
+    end
+    diff_label = 'unmerged'
+  elseif opts.untracked then
     old_lines = {}
     new_lines, err = git.get_working_content(filepath)
     if not new_lines then
@@ -236,6 +292,14 @@ function M.gdiff_file(filepath, opts)
   end
 
   M.setup_diff_buf(diff_buf)
+
+  if diff_label == 'unmerged' then
+    vim.api.nvim_buf_set_var(diff_buf, 'diffs_unmerged', true)
+    vim.api.nvim_buf_set_var(diff_buf, 'diffs_working_path', filepath)
+    local conflict_config = require('diffs').get_conflict_config()
+    require('diffs.merge').setup_keymaps(diff_buf, conflict_config)
+  end
+
   dbg('opened diff buffer %d for %s (%s)', diff_buf, rel_path, diff_label)
 
   vim.schedule(function()
@@ -263,6 +327,8 @@ function M.gdiff_section(repo_root, opts)
     return
   end
 
+  result = replace_combined_diffs(result, repo_root)
+
   if #result == 0 then
     vim.notify('[diffs.nvim]: no changes in section', vim.log.levels.INFO)
     return
@@ -325,6 +391,8 @@ function M.read_buffer(bufnr)
     if vim.v.shell_error ~= 0 then
       diff_lines = {}
     end
+
+    diff_lines = replace_combined_diffs(diff_lines, repo_root)
   else
     local abs_path = repo_root .. '/' .. path
 
@@ -334,7 +402,10 @@ function M.read_buffer(bufnr)
 
     local old_lines, new_lines
 
-    if label == 'untracked' then
+    if label == 'unmerged' then
+      old_lines = git.get_file_content(':2', abs_path) or {}
+      new_lines = git.get_file_content(':3', abs_path) or {}
+    elseif label == 'untracked' then
       old_lines = {}
       new_lines = git.get_working_content(abs_path) or {}
     elseif label == 'staged' then

lua/diffs/conflict.lua

@@ -20,8 +20,6 @@ local attached_buffers = {}
 ---@type table<integer, boolean>
 local diagnostics_suppressed = {}
 
-local PRIORITY_LINE_BG = 200
-
 ---@param lines string[]
 ---@return diffs.ConflictRegion[]
 function M.parse(lines)
@@ -92,6 +90,17 @@ local function parse_buffer(bufnr)
   return M.parse(lines)
 end
 
+---@param side string
+---@param config diffs.ConflictConfig
+---@return string?
+local function get_virtual_text_label(side, config)
+  if config.format_virtual_text then
+    local keymap = side == 'ours' and config.keymaps.ours or config.keymaps.theirs
+    return config.format_virtual_text(side, keymap)
+  end
+  return side == 'ours' and 'current' or 'incoming'
+end
+
 ---@param bufnr integer
 ---@param regions diffs.ConflictRegion[]
 ---@param config diffs.ConflictConfig
@@ -103,14 +112,41 @@ local function apply_highlights(bufnr, regions, config)
       end_row = region.marker_ours + 1,
       hl_group = 'DiffsConflictMarker',
       hl_eol = true,
-      priority = PRIORITY_LINE_BG,
+      priority = config.priority,
     })
 
     if config.show_virtual_text then
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_ours, 0, {
-        virt_text = { { ' (current)', 'DiffsConflictMarker' } },
-        virt_text_pos = 'eol',
-      })
+      local ours_label = get_virtual_text_label('ours', config)
+      if ours_label then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_ours, 0, {
+          virt_text = { { ' (' .. ours_label .. ')', 'DiffsConflictMarker' } },
+          virt_text_pos = 'eol',
+        })
+      end
+    end
+
+    if config.show_actions then
+      local parts = {}
+      local actions = {
+        { 'Current', config.keymaps.ours },
+        { 'Incoming', config.keymaps.theirs },
+        { 'Both', config.keymaps.both },
+        { 'None', config.keymaps.none },
+      }
+      for _, action in ipairs(actions) do
+        if action[2] then
+          if #parts > 0 then
+            table.insert(parts, { ' \226\148\130 ', 'DiffsConflictActions' })
+          end
+          table.insert(parts, { ('%s (%s)'):format(action[1], action[2]), 'DiffsConflictActions' })
+        end
+      end
+      if #parts > 0 then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_ours, 0, {
+          virt_lines = { parts },
+          virt_lines_above = true,
+        })
+      end
     end
 
     for line = region.ours_start, region.ours_end - 1 do
@@ -118,11 +154,11 @@ local function apply_highlights(bufnr, regions, config)
         end_row = line + 1,
         hl_group = 'DiffsConflictOurs',
         hl_eol = true,
-        priority = PRIORITY_LINE_BG,
+        priority = config.priority,
       })
       pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
         number_hl_group = 'DiffsConflictOursNr',
-        priority = PRIORITY_LINE_BG,
+        priority = config.priority,
       })
     end
 
@@ -131,7 +167,7 @@ local function apply_highlights(bufnr, regions, config)
         end_row = region.marker_base + 1,
         hl_group = 'DiffsConflictMarker',
         hl_eol = true,
-        priority = PRIORITY_LINE_BG,
+        priority = config.priority,
       })
 
       for line = region.base_start, region.base_end - 1 do
@@ -139,11 +175,11 @@ local function apply_highlights(bufnr, regions, config)
           end_row = line + 1,
           hl_group = 'DiffsConflictBase',
           hl_eol = true,
-          priority = PRIORITY_LINE_BG,
+          priority = config.priority,
         })
         pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
           number_hl_group = 'DiffsConflictBaseNr',
-          priority = PRIORITY_LINE_BG,
+          priority = config.priority,
         })
       end
     end
@@ -152,7 +188,7 @@ local function apply_highlights(bufnr, regions, config)
       end_row = region.marker_sep + 1,
       hl_group = 'DiffsConflictMarker',
       hl_eol = true,
-      priority = PRIORITY_LINE_BG,
+      priority = config.priority,
     })
 
     for line = region.theirs_start, region.theirs_end - 1 do
@@ -160,11 +196,11 @@ local function apply_highlights(bufnr, regions, config)
         end_row = line + 1,
         hl_group = 'DiffsConflictTheirs',
         hl_eol = true,
-        priority = PRIORITY_LINE_BG,
+        priority = config.priority,
       })
       pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, line, 0, {
         number_hl_group = 'DiffsConflictTheirsNr',
-        priority = PRIORITY_LINE_BG,
+        priority = config.priority,
       })
     end
 
@@ -172,14 +208,17 @@ local function apply_highlights(bufnr, regions, config)
       end_row = region.marker_theirs + 1,
       hl_group = 'DiffsConflictMarker',
       hl_eol = true,
-      priority = PRIORITY_LINE_BG,
+      priority = config.priority,
     })
 
     if config.show_virtual_text then
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_theirs, 0, {
-        virt_text = { { ' (incoming)', 'DiffsConflictMarker' } },
-        virt_text_pos = 'eol',
-      })
+      local theirs_label = get_virtual_text_label('theirs', config)
+      if theirs_label then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, region.marker_theirs, 0, {
+          virt_text = { { ' (' .. theirs_label .. ')', 'DiffsConflictMarker' } },
+          virt_text_pos = 'eol',
+        })
+      end
     end
   end
 end
@@ -199,7 +238,7 @@ end
 ---@param bufnr integer
 ---@param region diffs.ConflictRegion
 ---@param replacement string[]
-local function replace_region(bufnr, region, replacement)
+function M.replace_region(bufnr, region, replacement)
   vim.api.nvim_buf_set_lines(
     bufnr,
     region.marker_ours,
@@ -211,7 +250,7 @@ end
 
 ---@param bufnr integer
 ---@param config diffs.ConflictConfig
-local function refresh(bufnr, config)
+function M.refresh(bufnr, config)
   local regions = parse_buffer(bufnr)
   if #regions == 0 then
     vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
@@ -244,8 +283,8 @@ function M.resolve_ours(bufnr, config)
     return
   end
   local lines = vim.api.nvim_buf_get_lines(bufnr, region.ours_start, region.ours_end, false)
-  replace_region(bufnr, region, lines)
-  refresh(bufnr, config)
+  M.replace_region(bufnr, region, lines)
+  M.refresh(bufnr, config)
 end
 
 ---@param bufnr integer
@@ -262,8 +301,8 @@ function M.resolve_theirs(bufnr, config)
     return
   end
   local lines = vim.api.nvim_buf_get_lines(bufnr, region.theirs_start, region.theirs_end, false)
-  replace_region(bufnr, region, lines)
-  refresh(bufnr, config)
+  M.replace_region(bufnr, region, lines)
+  M.refresh(bufnr, config)
 end
 
 ---@param bufnr integer
@@ -288,8 +327,8 @@ function M.resolve_both(bufnr, config)
   for _, l in ipairs(theirs) do
     table.insert(combined, l)
   end
-  replace_region(bufnr, region, combined)
-  refresh(bufnr, config)
+  M.replace_region(bufnr, region, combined)
+  M.refresh(bufnr, config)
 end
 
 ---@param bufnr integer
@@ -305,8 +344,8 @@ function M.resolve_none(bufnr, config)
   if not region then
     return
   end
-  replace_region(bufnr, region, {})
-  refresh(bufnr, config)
+  M.replace_region(bufnr, region, {})
+  M.refresh(bufnr, config)
 end
 
 ---@param bufnr integer
@@ -323,6 +362,7 @@ function M.goto_next(bufnr)
       return
     end
   end
+  vim.notify('[diffs.nvim]: wrapped to first conflict', vim.log.levels.INFO)
   vim.api.nvim_win_set_cursor(0, { regions[1].marker_ours + 1, 0 })
 end
 
@@ -340,6 +380,7 @@ function M.goto_prev(bufnr)
       return
     end
   end
+  vim.notify('[diffs.nvim]: wrapped to last conflict', vim.log.levels.INFO)
   vim.api.nvim_win_set_cursor(0, { regions[#regions].marker_ours + 1, 0 })
 end
 
@@ -348,35 +389,19 @@ end
 local function setup_keymaps(bufnr, config)
   local km = config.keymaps
 
-  if km.ours then
-    vim.keymap.set('n', km.ours, function()
-      M.resolve_ours(bufnr, config)
-    end, { buffer = bufnr })
-  end
-  if km.theirs then
-    vim.keymap.set('n', km.theirs, function()
-      M.resolve_theirs(bufnr, config)
-    end, { buffer = bufnr })
-  end
-  if km.both then
-    vim.keymap.set('n', km.both, function()
-      M.resolve_both(bufnr, config)
-    end, { buffer = bufnr })
-  end
-  if km.none then
-    vim.keymap.set('n', km.none, function()
-      M.resolve_none(bufnr, config)
-    end, { buffer = bufnr })
-  end
-  if km.next then
-    vim.keymap.set('n', km.next, function()
-      M.goto_next(bufnr)
-    end, { buffer = bufnr })
-  end
-  if km.prev then
-    vim.keymap.set('n', km.prev, function()
-      M.goto_prev(bufnr)
-    end, { buffer = bufnr })
+  local maps = {
+    { km.ours, '<Plug>(diffs-conflict-ours)' },
+    { km.theirs, '<Plug>(diffs-conflict-theirs)' },
+    { km.both, '<Plug>(diffs-conflict-both)' },
+    { km.none, '<Plug>(diffs-conflict-none)' },
+    { km.next, '<Plug>(diffs-conflict-next)' },
+    { km.prev, '<Plug>(diffs-conflict-prev)' },
+  }
+
+  for _, map in ipairs(maps) do
+    if map[1] then
+      vim.keymap.set('n', map[1], map[2], { buffer = bufnr })
+    end
   end
 end
 
@@ -433,7 +458,7 @@ function M.attach(bufnr, config)
       if not attached_buffers[bufnr] then
         return true
       end
-      refresh(bufnr, config)
+      M.refresh(bufnr, config)
     end,
   })
 

lua/diffs/fugitive.lua

@@ -26,20 +26,65 @@ function M.get_section_at_line(bufnr, lnum)
   return nil
 end
 
+---@param s string
+---@return string
+local function unquote(s)
+  if s:sub(1, 1) ~= '"' then
+    return s
+  end
+  local inner = s:sub(2, -2)
+  local result = {}
+  local i = 1
+  while i <= #inner do
+    if inner:sub(i, i) == '\\' and i < #inner then
+      local next_char = inner:sub(i + 1, i + 1)
+      if next_char == 'n' then
+        table.insert(result, '\n')
+        i = i + 2
+      elseif next_char == 't' then
+        table.insert(result, '\t')
+        i = i + 2
+      elseif next_char == '"' then
+        table.insert(result, '"')
+        i = i + 2
+      elseif next_char == '\\' then
+        table.insert(result, '\\')
+        i = i + 2
+      elseif next_char:match('%d') then
+        local oct = inner:match('^(%d%d%d)', i + 1)
+        if oct then
+          table.insert(result, string.char(tonumber(oct, 8)))
+          i = i + 4
+        else
+          table.insert(result, next_char)
+          i = i + 2
+        end
+      else
+        table.insert(result, next_char)
+        i = i + 2
+      end
+    else
+      table.insert(result, inner:sub(i, i))
+      i = i + 1
+    end
+  end
+  return table.concat(result)
+end
+
 ---@param line string
----@return string?, string?
+---@return string?, string?, string?
 local function parse_file_line(line)
   local old, new = line:match('^R%d*%s+(.-)%s+->%s+(.+)$')
   if old and new then
-    return vim.trim(new), vim.trim(old)
+    return unquote(vim.trim(new)), unquote(vim.trim(old)), 'R'
   end
 
-  local filename = line:match('^[MADRCU?][MADRCU%s]*%s+(.+)$')
-  if filename then
-    return vim.trim(filename), nil
+  local status, filename = line:match('^([MADRCU?])[MADRCU%s]*%s+(.+)$')
+  if status and filename then
+    return unquote(vim.trim(filename)), nil, status
   end
 
-  return nil, nil
+  return nil, nil, nil
 end
 
 ---@param line string
@@ -57,34 +102,34 @@ end
 
 ---@param bufnr integer
 ---@param lnum integer
----@return string?, diffs.FugitiveSection, boolean, string?
+---@return string?, diffs.FugitiveSection, boolean, string?, string?
 function M.get_file_at_line(bufnr, lnum)
   local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
   local current_line = lines[lnum]
 
   if not current_line then
-    return nil, nil, false, nil
+    return nil, nil, false, nil, nil
   end
 
   local section_header = parse_section_header(current_line)
   if section_header then
-    return nil, section_header, true, nil
+    return nil, section_header, true, nil, nil
   end
 
-  local filename, old_filename = parse_file_line(current_line)
+  local filename, old_filename, status = parse_file_line(current_line)
   if filename then
     local section = M.get_section_at_line(bufnr, lnum)
-    return filename, section, false, old_filename
+    return filename, section, false, old_filename, status
   end
 
   local prefix = current_line:sub(1, 1)
   if prefix == '+' or prefix == '-' or prefix == ' ' then
     for i = lnum - 1, 1, -1 do
       local prev_line = lines[i]
-      filename, old_filename = parse_file_line(prev_line)
+      filename, old_filename, status = parse_file_line(prev_line)
       if filename then
         local section = M.get_section_at_line(bufnr, i)
-        return filename, section, false, old_filename
+        return filename, section, false, old_filename, status
       end
       if prev_line:match('^%w+ %(') or prev_line == '' then
         break
@@ -92,7 +137,7 @@ function M.get_file_at_line(bufnr, lnum)
     end
   end
 
-  return nil, nil, false, nil
+  return nil, nil, false, nil, nil
 end
 
 ---@class diffs.HunkPosition
@@ -150,7 +195,7 @@ function M.diff_file_under_cursor(vertical)
   local bufnr = vim.api.nvim_get_current_buf()
   local lnum = vim.api.nvim_win_get_cursor(0)[1]
 
-  local filename, section, is_header, old_filename = M.get_file_at_line(bufnr, lnum)
+  local filename, section, is_header, old_filename, status = M.get_file_at_line(bufnr, lnum)
 
   local repo_root = get_repo_root_from_fugitive(bufnr)
   if not repo_root then
@@ -192,6 +237,7 @@ function M.diff_file_under_cursor(vertical)
     vertical = vertical,
     staged = section == 'staged',
     untracked = section == 'untracked',
+    unmerged = status == 'U',
     old_filepath = old_filepath,
     hunk_position = hunk_position,
   })

lua/diffs/git.lua

@@ -1,13 +1,19 @@
 local M = {}
 
+local repo_root_cache = {}
+
 ---@param filepath string
 ---@return string?
 function M.get_repo_root(filepath)
   local dir = vim.fn.fnamemodify(filepath, ':h')
+  if repo_root_cache[dir] ~= nil then
+    return repo_root_cache[dir]
+  end
   local result = vim.fn.systemlist({ 'git', '-C', dir, 'rev-parse', '--show-toplevel' })
   if vim.v.shell_error ~= 0 then
     return nil
   end
+  repo_root_cache[dir] = result[1]
   return result[1]
 end
 

lua/diffs/gitsigns.lua

@@ -0,0 +1,172 @@
+local M = {}
+
+local api = vim.api
+local fn = vim.fn
+local dbg = require('diffs.log').dbg
+
+local ns = api.nvim_create_namespace('diffs-gitsigns')
+local gs_popup_ns = api.nvim_create_namespace('gitsigns_popup')
+
+local patched = false
+
+---@param bufnr integer
+---@param src_filename string
+---@param src_ft string?
+---@param src_lang string?
+---@return diffs.Hunk[]
+function M.parse_blame_hunks(bufnr, src_filename, src_ft, src_lang)
+  local lines = api.nvim_buf_get_lines(bufnr, 0, -1, false)
+  local hunks = {}
+  local hunk_lines = {}
+  local hunk_start = nil
+
+  for i, line in ipairs(lines) do
+    if line:match('^Hunk %d+ of %d+') then
+      if hunk_start and #hunk_lines > 0 then
+        table.insert(hunks, {
+          filename = src_filename,
+          ft = src_ft,
+          lang = src_lang,
+          start_line = hunk_start,
+          prefix_width = 1,
+          quote_width = 0,
+          lines = hunk_lines,
+        })
+      end
+      hunk_lines = {}
+      hunk_start = i
+    elseif hunk_start then
+      if line:match('^%(guessed:') then
+        hunk_start = i
+      else
+        local prefix = line:sub(1, 1)
+        if prefix == ' ' or prefix == '+' or prefix == '-' then
+          if #hunk_lines == 0 then
+            hunk_start = i - 1
+          end
+          table.insert(hunk_lines, line)
+        end
+      end
+    end
+  end
+
+  if hunk_start and #hunk_lines > 0 then
+    table.insert(hunks, {
+      filename = src_filename,
+      ft = src_ft,
+      lang = src_lang,
+      start_line = hunk_start,
+      prefix_width = 1,
+      quote_width = 0,
+      lines = hunk_lines,
+    })
+  end
+
+  return hunks
+end
+
+---@param preview_winid integer
+---@param preview_bufnr integer
+local function on_preview(preview_winid, preview_bufnr)
+  local ok, err = pcall(function()
+    if not api.nvim_buf_is_valid(preview_bufnr) then
+      return
+    end
+    if not api.nvim_win_is_valid(preview_winid) then
+      return
+    end
+
+    local win = api.nvim_get_current_win()
+    if win == preview_winid then
+      win = fn.win_getid(fn.winnr('#'))
+    end
+    if win == -1 or win == 0 or not api.nvim_win_is_valid(win) then
+      return
+    end
+
+    local srcbuf = api.nvim_win_get_buf(win)
+    if not api.nvim_buf_is_loaded(srcbuf) then
+      return
+    end
+
+    local ft = vim.bo[srcbuf].filetype
+    local name = api.nvim_buf_get_name(srcbuf)
+    if not name or name == '' then
+      name = ft and ('a.' .. ft) or 'unknown'
+    end
+    local lang = ft and require('diffs.parser').get_lang_from_ft(ft) or nil
+
+    local hunks = M.parse_blame_hunks(preview_bufnr, name, ft, lang)
+    if #hunks == 0 then
+      return
+    end
+
+    local diff_start = hunks[1].start_line
+    local last = hunks[#hunks]
+    local diff_end = last.start_line + #last.lines
+
+    api.nvim_buf_clear_namespace(preview_bufnr, gs_popup_ns, diff_start, diff_end)
+    api.nvim_buf_clear_namespace(preview_bufnr, ns, diff_start, diff_end)
+
+    local opts = require('diffs').get_highlight_opts()
+    local highlight = require('diffs.highlight')
+    for _, hunk in ipairs(hunks) do
+      highlight.highlight_hunk(preview_bufnr, ns, hunk, opts)
+      for j, line in ipairs(hunk.lines) do
+        local ch = line:sub(1, 1)
+        if ch == '+' or ch == '-' then
+          pcall(api.nvim_buf_set_extmark, preview_bufnr, ns, hunk.start_line + j - 1, 0, {
+            end_col = 1,
+            hl_group = ch == '+' and '@diff.plus' or '@diff.minus',
+            priority = opts.highlights.priorities.syntax,
+          })
+        end
+      end
+    end
+
+    dbg('gitsigns blame: highlighted %d hunks in popup buf %d', #hunks, preview_bufnr)
+  end)
+  if not ok then
+    dbg('gitsigns blame error: %s', err)
+  end
+end
+
+---@return boolean
+function M.setup()
+  if patched then
+    return true
+  end
+
+  local pop_ok, Popup = pcall(require, 'gitsigns.popup')
+  if not pop_ok or not Popup then
+    return false
+  end
+
+  Popup.create = (function(orig)
+    return function(...)
+      local winid, bufnr = orig(...)
+      on_preview(winid, bufnr)
+      return winid, bufnr
+    end
+  end)(Popup.create)
+
+  Popup.update = (function(orig)
+    return function(winid, bufnr, ...)
+      orig(winid, bufnr, ...)
+      on_preview(winid, bufnr)
+    end
+  end)(Popup.update)
+
+  patched = true
+  dbg('gitsigns popup patched')
+  return true
+end
+
+M._test = {
+  parse_blame_hunks = M.parse_blame_hunks,
+  on_preview = on_preview,
+  ns = ns,
+  gs_popup_ns = gs_popup_ns,
+}
+
+return M

lua/diffs/highlight.lua

@@ -3,38 +3,6 @@ local M = {}
 local dbg = require('diffs.log').dbg
 local diff = require('diffs.diff')
 
----@param filepath string
----@param from_line integer
----@param count integer
----@return string[]
-local function read_line_range(filepath, from_line, count)
-  if count <= 0 then
-    return {}
-  end
-  local f = io.open(filepath, 'r')
-  if not f then
-    return {}
-  end
-  local result = {}
-  local line_num = 0
-  for line in f:lines() do
-    line_num = line_num + 1
-    if line_num >= from_line then
-      table.insert(result, line)
-      if #result >= count then
-        break
-      end
-    end
-  end
-  f:close()
-  return result
-end
-
-local PRIORITY_CLEAR = 198
-local PRIORITY_SYNTAX = 199
-local PRIORITY_LINE_BG = 200
-local PRIORITY_CHAR_BG = 201
-
 ---@param bufnr integer
 ---@param ns integer
 ---@param hunk diffs.Hunk
@@ -42,8 +10,9 @@ local PRIORITY_CHAR_BG = 201
 ---@param text string
 ---@param lang string
 ---@param context_lines? string[]
+---@param priorities diffs.PrioritiesConfig
 ---@return integer
-local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_lines)
+local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_lines, priorities)
   local parse_text = text
   if context_lines and #context_lines > 0 then
     parse_text = text .. '\n' .. table.concat(context_lines, '\n')
@@ -77,7 +46,7 @@ local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_l
       local buf_sc = col_offset + sc
       local buf_ec = col_offset + ec
 
-      local priority = lang == 'diff' and (tonumber(metadata.priority) or 100) or PRIORITY_SYNTAX
+      local priority = lang == 'diff' and (tonumber(metadata.priority) or 100) or priorities.syntax
 
       pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_sr, buf_sc, {
         end_row = buf_er,
@@ -95,6 +64,12 @@ end
 ---@class diffs.HunkOpts
 ---@field hide_prefix boolean
 ---@field highlights diffs.Highlights
+---@field defer_vim_syntax? boolean
+---@field syntax_only? boolean
+
+---@class diffs.TSContext
+---@field before string[]?
+---@field after string[]?
 
 ---@param bufnr integer
 ---@param ns integer
@@ -103,6 +78,9 @@ end
 ---@param line_map table<integer, integer>
 ---@param col_offset integer
 ---@param covered_lines? table<integer, true>
+---@param priorities diffs.PrioritiesConfig
+---@param force_high_priority? boolean
+---@param context? diffs.TSContext
 ---@return integer
 local function highlight_treesitter(
   bufnr,
@@ -111,9 +89,36 @@ local function highlight_treesitter(
   lang,
   line_map,
   col_offset,
-  covered_lines
+  covered_lines,
+  priorities,
+  force_high_priority,
+  context
 )
-  local code = table.concat(code_lines, '\n')
+  local prefix_count = 0
+  local parse_lines = code_lines
+  if context then
+    local before = context.before
+    local after = context.after
+    if (before and #before > 0) or (after and #after > 0) then
+      parse_lines = {}
+      if before then
+        prefix_count = #before
+        for _, l in ipairs(before) do
+          parse_lines[#parse_lines + 1] = l
+        end
+      end
+      for _, l in ipairs(code_lines) do
+        parse_lines[#parse_lines + 1] = l
+      end
+      if after then
+        for _, l in ipairs(after) do
+          parse_lines[#parse_lines + 1] = l
+        end
+      end
+    end
+  end
+
+  local code = table.concat(parse_lines, '\n')
   if code == '' then
     return 0
   end
@@ -143,6 +148,8 @@ local function highlight_treesitter(
       if capture ~= 'spell' and capture ~= 'nospell' then
         local capture_name = '@' .. capture .. '.' .. tree_lang
         local sr, sc, er, ec = node:range()
+        sr = sr - prefix_count
+        er = er - prefix_count
 
         local buf_sr = line_map[sr]
         if buf_sr then
@@ -151,8 +158,10 @@ local function highlight_treesitter(
           local buf_sc = sc + col_offset
           local buf_ec = ec + col_offset
 
-          local priority = tree_lang == 'diff' and (tonumber(metadata.priority) or 100)
-            or PRIORITY_SYNTAX
+          local meta_prio = tonumber(metadata.priority) or 100
+          local priority = tree_lang == 'diff'
+              and ((col_offset > 0 or force_high_priority) and (priorities.syntax + meta_prio - 100) or meta_prio)
+            or priorities.syntax
 
           pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_sr, buf_sc, {
             end_row = buf_er,
@@ -219,8 +228,17 @@ end
 ---@param code_lines string[]
 ---@param covered_lines? table<integer, true>
 ---@param leading_offset? integer
+---@param priorities diffs.PrioritiesConfig
 ---@return integer
-local function highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines, leading_offset)
+local function highlight_vim_syntax(
+  bufnr,
+  ns,
+  hunk,
+  code_lines,
+  covered_lines,
+  leading_offset,
+  priorities
+)
   local ft = hunk.ft
   if not ft then
     return 0
@@ -238,9 +256,9 @@ local function highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines,
 
   local spans = {}
 
-  vim.api.nvim_buf_call(scratch, function()
+  pcall(vim.api.nvim_buf_call, scratch, function()
     vim.cmd('setlocal syntax=' .. ft)
-    vim.cmd('redraw')
+    vim.cmd.redraw()
 
     ---@param line integer
     ---@param col integer
@@ -256,18 +274,19 @@ local function highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines,
     spans = M.coalesce_syntax_spans(query_fn, code_lines)
   end)
 
-  vim.api.nvim_buf_delete(scratch, { force = true })
+  pcall(vim.api.nvim_buf_delete, scratch, { force = true })
 
   local hunk_line_count = #hunk.lines
+  local col_off = (hunk.prefix_width or 1) + (hunk.quote_width or 0) - 1
   local extmark_count = 0
   for _, span in ipairs(spans) do
     local adj = span.line - leading_offset
     if adj >= 1 and adj <= hunk_line_count then
       local buf_line = hunk.start_line + adj - 1
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
-        end_col = span.col_end,
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start + col_off, {
+        end_col = span.col_end + col_off,
         hl_group = span.hl_name,
-        priority = PRIORITY_SYNTAX,
+        priority = priorities.syntax,
       })
       extmark_count = extmark_count + 1
       if covered_lines then
@@ -284,44 +303,47 @@ end
 ---@param hunk diffs.Hunk
 ---@param opts diffs.HunkOpts
 function M.highlight_hunk(bufnr, ns, hunk, opts)
+  local p = opts.highlights.priorities
+  local pw = hunk.prefix_width or 1
+  local qw = hunk.quote_width or 0
   local use_ts = hunk.lang and opts.highlights.treesitter.enabled
   local use_vim = not use_ts and hunk.ft and opts.highlights.vim.enabled
 
   local max_lines = use_ts and opts.highlights.treesitter.max_lines or opts.highlights.vim.max_lines
-  if (use_ts or use_vim) and #hunk.lines > max_lines then
-    dbg(
-      'skipping hunk %s:%d (%d lines > %d max)',
-      hunk.filename,
-      hunk.start_line,
-      #hunk.lines,
-      max_lines
-    )
-    use_ts = false
+  if use_ts or use_vim then
+    local hl_count = 0
+    for _, line in ipairs(hunk.lines) do
+      local c = line:sub(1, 1)
+      if c == '+' or c == '-' then
+        hl_count = hl_count + 1
+      end
+    end
+    hunk._hl_line_count = hl_count
+    if hl_count > max_lines then
+      dbg(
+        'skipping hunk %s:%d (%d highlighted lines > %d max)',
+        hunk.filename,
+        hunk.start_line,
+        hl_count,
+        max_lines
+      )
+      use_ts = false
+      use_vim = false
+    end
+  end
+
+  if use_vim and opts.defer_vim_syntax then
     use_vim = false
   end
 
   ---@type table<integer, true>
   local covered_lines = {}
 
-  local ctx_cfg = opts.highlights.context
-  local context = (ctx_cfg and ctx_cfg.enabled) and ctx_cfg.lines or 0
-  local leading = {}
-  local trailing = {}
-  if (use_ts or use_vim) and context > 0 and hunk.file_new_start and hunk.repo_root then
-    local filepath = vim.fs.joinpath(hunk.repo_root, hunk.filename)
-    local lead_from = math.max(1, hunk.file_new_start - context)
-    local lead_count = hunk.file_new_start - lead_from
-    if lead_count > 0 then
-      leading = read_line_range(filepath, lead_from, lead_count)
-    end
-    local trail_from = hunk.file_new_start + (hunk.file_new_count or 0)
-    trailing = read_line_range(filepath, trail_from, context)
-  end
-
   local extmark_count = 0
+  ---@type string[]
+  local new_code = {}
+
   if use_ts then
-    ---@type string[]
-    local new_code = {}
     ---@type table<integer, integer>
     local new_map = {}
     ---@type string[]
@@ -329,20 +351,17 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     ---@type table<integer, integer>
     local old_map = {}
 
-    for _, pad_line in ipairs(leading) do
-      table.insert(new_code, pad_line)
-      table.insert(old_code, pad_line)
-    end
-
     for i, line in ipairs(hunk.lines) do
-      local prefix = line:sub(1, 1)
-      local stripped = line:sub(2)
+      local prefix = line:sub(1, pw)
+      local stripped = line:sub(pw + 1)
       local buf_line = hunk.start_line + i - 1
+      local has_add = prefix:find('+', 1, true) ~= nil
+      local has_del = prefix:find('-', 1, true) ~= nil
 
-      if prefix == '+' then
+      if has_add and not has_del then
         new_map[#new_code] = buf_line
         table.insert(new_code, stripped)
-      elseif prefix == '-' then
+      elseif has_del and not has_add then
         old_map[#old_code] = buf_line
         table.insert(old_code, stripped)
       else
@@ -352,22 +371,38 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       end
     end
 
-    for _, pad_line in ipairs(trailing) do
-      table.insert(new_code, pad_line)
-      table.insert(old_code, pad_line)
+    local ts_context = nil
+    if opts.highlights.context.enabled and (hunk.context_before or hunk.context_after) then
+      ts_context = { before = hunk.context_before, after = hunk.context_after }
     end
 
-    extmark_count = highlight_treesitter(bufnr, ns, new_code, hunk.lang, new_map, 1, covered_lines)
+    extmark_count = highlight_treesitter(
+      bufnr,
+      ns,
+      new_code,
+      hunk.lang,
+      new_map,
+      pw + qw,
+      covered_lines,
+      p,
+      nil,
+      ts_context
+    )
     extmark_count = extmark_count
-      + highlight_treesitter(bufnr, ns, old_code, hunk.lang, old_map, 1, covered_lines)
+      + highlight_treesitter(
+        bufnr,
+        ns,
+        old_code,
+        hunk.lang,
+        old_map,
+        pw + qw,
+        covered_lines,
+        p,
+        nil,
+        ts_context
+      )
 
     if hunk.header_context and hunk.header_context_col then
-      local header_line = hunk.start_line - 1
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, header_line, hunk.header_context_col, {
-        end_col = hunk.header_context_col + #hunk.header_context,
-        hl_group = 'DiffsClear',
-        priority = PRIORITY_CLEAR,
-      })
       local header_extmarks = highlight_text(
         bufnr,
         ns,
@@ -375,7 +410,8 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
         hunk.header_context_col,
         hunk.header_context,
         hunk.lang,
-        new_code
+        new_code,
+        p
       )
       if header_extmarks > 0 then
         dbg('header %s:%d applied %d extmarks', hunk.filename, hunk.start_line, header_extmarks)
@@ -385,16 +421,10 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
   elseif use_vim then
     ---@type string[]
     local code_lines = {}
-    for _, pad_line in ipairs(leading) do
-      table.insert(code_lines, pad_line)
-    end
     for _, line in ipairs(hunk.lines) do
-      table.insert(code_lines, line:sub(2))
+      table.insert(code_lines, line:sub(pw + 1))
     end
-    for _, pad_line in ipairs(trailing) do
-      table.insert(code_lines, pad_line)
-    end
-    extmark_count = highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines, #leading)
+    extmark_count = highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines, 0, p)
   end
 
   if
@@ -409,13 +439,35 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       header_map[i] = hunk.header_start_line - 1 + i
     end
     extmark_count = extmark_count
-      + highlight_treesitter(bufnr, ns, hunk.header_lines, 'diff', header_map, 0)
+      + highlight_treesitter(
+        bufnr,
+        ns,
+        hunk.header_lines,
+        'diff',
+        header_map,
+        qw,
+        nil,
+        p,
+        qw > 0 or pw > 1
+      )
+  end
+
+  local at_raw_line
+  if (qw > 0 or pw > 1) and opts.highlights.treesitter.enabled then
+    local at_buf_line = hunk.start_line - 1
+    at_raw_line = vim.api.nvim_buf_get_lines(bufnr, at_buf_line, at_buf_line + 1, false)[1]
   end
 
   ---@type diffs.IntraChanges?
   local intra = nil
   local intra_cfg = opts.highlights.intra
-  if intra_cfg and intra_cfg.enabled and #hunk.lines <= intra_cfg.max_lines then
+  if
+    not opts.syntax_only
+    and intra_cfg
+    and intra_cfg.enabled
+    and pw == 1
+    and (hunk._hl_line_count or #hunk.lines) <= intra_cfg.max_lines
+  then
     dbg('computing intra for hunk %s:%d (%d lines)', hunk.filename, hunk.start_line, #hunk.lines)
     intra = diff.compute_intra_hunks(hunk.lines, intra_cfg.algorithm)
     if intra then
@@ -425,8 +477,8 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     end
   elseif intra_cfg and not intra_cfg.enabled then
     dbg('intra disabled by config')
-  elseif intra_cfg and #hunk.lines > intra_cfg.max_lines then
-    dbg('intra skipped: %d lines > %d max', #hunk.lines, intra_cfg.max_lines)
+  elseif intra_cfg and (hunk._hl_line_count or #hunk.lines) > intra_cfg.max_lines then
+    dbg('intra skipped: %d highlighted lines > %d max', hunk._hl_line_count or #hunk.lines, intra_cfg.max_lines)
   end
 
   ---@type table<integer, diffs.CharSpan[]>
@@ -446,68 +498,186 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
     end
   end
 
+  if
+    (qw > 0 or pw > 1)
+    and hunk.header_start_line
+    and hunk.header_lines
+    and #hunk.header_lines > 0
+    and opts.highlights.treesitter.enabled
+  then
+    for i = 0, #hunk.header_lines - 1 do
+      local buf_line = hunk.header_start_line - 1 + i
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
+        end_col = #hunk.header_lines[i + 1] + qw,
+        hl_group = 'DiffsClear',
+        priority = p.clear,
+      })
+
+      if pw > 1 then
+        local hline = hunk.header_lines[i + 1]
+        if hline:match('^index ') then
+          pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, qw, {
+            end_col = 5 + qw,
+            hl_group = '@keyword.diff',
+            priority = p.syntax,
+          })
+          local dot_pos = hline:find('%.%.', 1, false)
+          if dot_pos then
+            local rest = hline:sub(dot_pos + 2)
+            local hash = rest:match('^(%x+)')
+            if hash then
+              pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, dot_pos + 1 + qw, {
+                end_col = dot_pos + 1 + #hash + qw,
+                hl_group = '@constant.diff',
+                priority = p.syntax,
+              })
+            end
+          end
+        end
+      end
+    end
+  end
+
+  if (qw > 0 or pw > 1) and at_raw_line then
+    local at_buf_line = hunk.start_line - 1
+    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, at_buf_line, 0, {
+      end_col = #at_raw_line,
+      hl_group = 'DiffsClear',
+      priority = p.clear,
+    })
+    if opts.highlights.treesitter.enabled then
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, at_buf_line, qw, {
+        end_col = #at_raw_line,
+        hl_group = '@attribute.diff',
+        priority = p.syntax,
+      })
+    end
+  end
+
+  if use_ts and hunk.header_context and hunk.header_context_col then
+    local header_line = hunk.start_line - 1
+    pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, header_line, hunk.header_context_col, {
+      end_col = hunk.header_context_col + #hunk.header_context,
+      hl_group = 'DiffsClear',
+      priority = p.clear,
+    })
+  end
+
+  local raw_body_lines
+  if qw > 0 then
+    raw_body_lines =
+      vim.api.nvim_buf_get_lines(bufnr, hunk.start_line, hunk.start_line + #hunk.lines, false)
+  end
+
   for i, line in ipairs(hunk.lines) do
     local buf_line = hunk.start_line + i - 1
     local line_len = #line
-    local prefix = line:sub(1, 1)
+    local raw_len = raw_body_lines and #raw_body_lines[i] or nil
+    local prefix = line:sub(1, pw)
+    local has_add = prefix:find('+', 1, true) ~= nil
+    local has_del = prefix:find('-', 1, true) ~= nil
+    local is_diff_line = has_add or has_del
+    local line_hl = is_diff_line and (has_add and 'DiffsAdd' or 'DiffsDelete') or nil
+    local number_hl = is_diff_line and (has_add and 'DiffsAddNr' or 'DiffsDeleteNr') or nil
 
-    local is_diff_line = prefix == '+' or prefix == '-'
-    local line_hl = is_diff_line and (prefix == '+' and 'DiffsAdd' or 'DiffsDelete') or nil
-    local number_hl = is_diff_line and (prefix == '+' and 'DiffsAddNr' or 'DiffsDeleteNr') or nil
-
-    if opts.hide_prefix then
-      local virt_hl = (opts.highlights.background and line_hl) or nil
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-        virt_text = { { ' ', virt_hl } },
-        virt_text_pos = 'overlay',
-      })
+    local is_marker = false
+    if pw > 1 and line_hl and not prefix:find('[^+]') then
+      local content = line:sub(pw + 1)
+      is_marker = content:match('^<<<<<<<')
+        or content:match('^=======')
+        or content:match('^>>>>>>>')
+        or content:match('^|||||||')
     end
 
-    if line_len > 1 and covered_lines[buf_line] then
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 1, {
-        end_col = line_len,
-        hl_group = 'DiffsClear',
-        priority = PRIORITY_CLEAR,
-      })
-    end
-
-    if opts.highlights.background and is_diff_line then
-      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-        end_row = buf_line + 1,
-        hl_group = line_hl,
-        hl_eol = true,
-        priority = PRIORITY_LINE_BG,
-      })
-      if opts.highlights.gutter then
+    if not opts.syntax_only then
+      if opts.hide_prefix then
+        local virt_hl = (opts.highlights.background and line_hl) or nil
         pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
-          number_hl_group = number_hl,
-          priority = PRIORITY_LINE_BG,
+          virt_text = { { string.rep(' ', pw + qw), virt_hl } },
+          virt_text_pos = 'overlay',
         })
       end
+
+      if qw > 0 or pw > 1 then
+        local prefix_end = pw + qw
+        if raw_len and prefix_end > raw_len then
+          prefix_end = raw_len
+        end
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
+          end_col = prefix_end,
+          hl_group = 'DiffsClear',
+          priority = p.clear,
+        })
+        for ci = 0, pw - 1 do
+          local ch = line:sub(ci + 1, ci + 1)
+          if ch == '+' or ch == '-' then
+            local char_col = ci + qw
+            if raw_len and char_col >= raw_len then
+              break
+            end
+            pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, char_col, {
+              end_col = char_col + 1,
+              hl_group = ch == '+' and '@diff.plus' or '@diff.minus',
+              priority = p.syntax,
+            })
+          end
+        end
+      elseif opts.highlights.background and is_diff_line then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
+          end_col = 1,
+          hl_group = number_hl,
+          priority = p.syntax,
+        })
+      end
+
+      if opts.highlights.background and is_diff_line then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
+          line_hl_group = line_hl,
+          number_hl_group = opts.highlights.gutter and number_hl or nil,
+          priority = p.line_bg,
+        })
+      end
+
+      if is_marker and line_len > pw then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw + qw, {
+          end_col = line_len + qw,
+          hl_group = 'DiffsConflictMarker',
+          priority = p.char_bg,
+        })
+      end
+
+      if char_spans_by_line[i] then
+        local char_hl = has_add and 'DiffsAddText' or 'DiffsDeleteText'
+        for _, span in ipairs(char_spans_by_line[i]) do
+          dbg(
+            'char extmark: line=%d buf_line=%d col=%d..%d hl=%s text="%s"',
+            i,
+            buf_line,
+            span.col_start,
+            span.col_end,
+            char_hl,
+            line:sub(span.col_start + 1, span.col_end)
+          )
+          local ok, err =
+            pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start + qw, {
+              end_col = span.col_end + qw,
+              hl_group = char_hl,
+              priority = p.char_bg,
+            })
+          if not ok then
+            dbg('char extmark FAILED: %s', err)
+          end
+          extmark_count = extmark_count + 1
+        end
+      end
     end
 
-    if char_spans_by_line[i] then
-      local char_hl = prefix == '+' and 'DiffsAddText' or 'DiffsDeleteText'
-      for _, span in ipairs(char_spans_by_line[i]) do
-        dbg(
-          'char extmark: line=%d buf_line=%d col=%d..%d hl=%s text="%s"',
-          i,
-          buf_line,
-          span.col_start,
-          span.col_end,
-          char_hl,
-          line:sub(span.col_start + 1, span.col_end)
-        )
-        local ok, err = pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
-          end_col = span.col_end,
-          hl_group = char_hl,
-          priority = PRIORITY_CHAR_BG,
-        })
-        if not ok then
-          dbg('char extmark FAILED: %s', err)
-        end
-        extmark_count = extmark_count + 1
-      end
+    if line_len > pw and covered_lines[buf_line] then
+      pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw + qw, {
+        end_col = line_len + qw,
+        hl_group = 'DiffsClear',
+        priority = p.clear,
+      })
     end
   end
 

lua/diffs/lib.lua

@@ -8,6 +8,9 @@ local cached_handle = nil
 ---@type boolean
 local download_in_progress = false
 
+---@type fun(handle: table?)[]
+local pending_callbacks = {}
+
 ---@return string
 local function get_os()
   local os_name = jit.os:lower()
@@ -164,9 +167,10 @@ function M.ensure(callback)
     return
   end
 
+  table.insert(pending_callbacks, callback)
+
   if download_in_progress then
-    dbg('download already in progress')
-    callback(nil)
+    dbg('download already in progress, queued callback')
     return
   end
 
@@ -192,21 +196,25 @@ function M.ensure(callback)
   vim.system(cmd, {}, function(result)
     download_in_progress = false
     vim.schedule(function()
+      local handle = nil
       if result.code ~= 0 then
         vim.notify('[diffs] failed to download libvscode_diff', vim.log.levels.WARN)
         dbg('curl failed: %s', result.stderr or '')
-        callback(nil)
-        return
+      else
+        local f = io.open(version_path(), 'w')
+        if f then
+          f:write(EXPECTED_VERSION)
+          f:close()
+        end
+        vim.notify('[diffs] libvscode_diff downloaded', vim.log.levels.INFO)
+        handle = M.load()
       end
 
-      local f = io.open(version_path(), 'w')
-      if f then
-        f:write(EXPECTED_VERSION)
-        f:close()
+      local cbs = pending_callbacks
+      pending_callbacks = {}
+      for _, cb in ipairs(cbs) do
+        cb(handle)
       end
-
-      vim.notify('[diffs] libvscode_diff downloaded', vim.log.levels.INFO)
-      callback(M.load())
     end)
   end)
 end

lua/diffs/log.lua

@@ -1,10 +1,17 @@
 local M = {}
 
 local enabled = false
+local log_file = nil
 
----@param val boolean
+---@param val boolean|string
 function M.set_enabled(val)
-  enabled = val
+  if type(val) == 'string' then
+    enabled = true
+    log_file = val
+  else
+    enabled = val
+    log_file = nil
+  end
 end
 
 ---@param msg string
@@ -13,7 +20,16 @@ function M.dbg(msg, ...)
   if not enabled then
     return
   end
-  vim.notify('[diffs.nvim]: ' .. string.format(msg, ...), vim.log.levels.DEBUG)
+  local formatted = '[diffs.nvim]: ' .. string.format(msg, ...)
+  if log_file then
+    local f = io.open(log_file, 'a')
+    if f then
+      f:write(string.format('%.6fs', vim.uv.hrtime() / 1e9) .. ' ' .. formatted .. '\n')
+      f:close()
+    end
+  else
+    vim.notify(formatted, vim.log.levels.DEBUG)
+  end
 end
 
 return M

lua/diffs/merge.lua

@@ -0,0 +1,418 @@
+local M = {}
+
+local conflict = require('diffs.conflict')
+
+local ns = vim.api.nvim_create_namespace('diffs-merge')
+
+---@type table<integer, table<integer, true>>
+local resolved_hunks = {}
+
+---@class diffs.MergeHunkInfo
+---@field index integer
+---@field start_line integer
+---@field end_line integer
+---@field del_lines string[]
+---@field add_lines string[]
+
+---@param bufnr integer
+---@return diffs.MergeHunkInfo[]
+function M.parse_hunks(bufnr)
+  local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
+  local hunks = {}
+  local current = nil
+
+  for i, line in ipairs(lines) do
+    local idx = i - 1
+    if line:match('^@@') then
+      if current then
+        current.end_line = idx - 1
+        table.insert(hunks, current)
+      end
+      current = {
+        index = #hunks + 1,
+        start_line = idx,
+        end_line = idx,
+        del_lines = {},
+        add_lines = {},
+      }
+    elseif current then
+      local prefix = line:sub(1, 1)
+      if prefix == '-' then
+        table.insert(current.del_lines, line:sub(2))
+      elseif prefix == '+' then
+        table.insert(current.add_lines, line:sub(2))
+      elseif prefix ~= ' ' and prefix ~= '\\' then
+        current.end_line = idx - 1
+        table.insert(hunks, current)
+        current = nil
+      end
+      if current then
+        current.end_line = idx
+      end
+    end
+  end
+
+  if current then
+    table.insert(hunks, current)
+  end
+
+  return hunks
+end
+
+---@param bufnr integer
+---@return diffs.MergeHunkInfo?
+function M.find_hunk_at_cursor(bufnr)
+  local hunks = M.parse_hunks(bufnr)
+  local cursor_line = vim.api.nvim_win_get_cursor(0)[1] - 1
+
+  for _, hunk in ipairs(hunks) do
+    if cursor_line >= hunk.start_line and cursor_line <= hunk.end_line then
+      return hunk
+    end
+  end
+
+  return nil
+end
+
+---@param hunk diffs.MergeHunkInfo
+---@param working_bufnr integer
+---@return diffs.ConflictRegion?
+function M.match_hunk_to_conflict(hunk, working_bufnr)
+  local working_lines = vim.api.nvim_buf_get_lines(working_bufnr, 0, -1, false)
+  local regions = conflict.parse(working_lines)
+
+  for _, region in ipairs(regions) do
+    local ours_lines = {}
+    for line = region.ours_start + 1, region.ours_end do
+      table.insert(ours_lines, working_lines[line])
+    end
+
+    if #ours_lines == #hunk.del_lines then
+      local match = true
+      for j = 1, #ours_lines do
+        if ours_lines[j] ~= hunk.del_lines[j] then
+          match = false
+          break
+        end
+      end
+      if match then
+        return region
+      end
+    end
+  end
+
+  return nil
+end
+
+---@param diff_bufnr integer
+---@return integer?
+function M.get_or_load_working_buf(diff_bufnr)
+  local ok, working_path = pcall(vim.api.nvim_buf_get_var, diff_bufnr, 'diffs_working_path')
+  if not ok or not working_path then
+    return nil
+  end
+
+  local existing = vim.fn.bufnr(working_path)
+  if existing ~= -1 then
+    return existing
+  end
+
+  local bufnr = vim.fn.bufadd(working_path)
+  vim.fn.bufload(bufnr)
+  return bufnr
+end
+
+---@param diff_bufnr integer
+---@param hunk_index integer
+local function mark_resolved(diff_bufnr, hunk_index)
+  if not resolved_hunks[diff_bufnr] then
+    resolved_hunks[diff_bufnr] = {}
+  end
+  resolved_hunks[diff_bufnr][hunk_index] = true
+end
+
+---@param diff_bufnr integer
+---@param hunk_index integer
+---@return boolean
+function M.is_resolved(diff_bufnr, hunk_index)
+  return resolved_hunks[diff_bufnr] and resolved_hunks[diff_bufnr][hunk_index] or false
+end
+
+---@param diff_bufnr integer
+---@param hunk diffs.MergeHunkInfo
+local function add_resolved_virtual_text(diff_bufnr, hunk)
+  pcall(vim.api.nvim_buf_set_extmark, diff_bufnr, ns, hunk.start_line, 0, {
+    virt_text = { { ' (resolved)', 'Comment' } },
+    virt_text_pos = 'eol',
+  })
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_ours(bufnr, config)
+  local hunk = M.find_hunk_at_cursor(bufnr)
+  if not hunk then
+    return
+  end
+  if M.is_resolved(bufnr, hunk.index) then
+    vim.notify('[diffs.nvim]: hunk already resolved', vim.log.levels.INFO)
+    return
+  end
+  local working_bufnr = M.get_or_load_working_buf(bufnr)
+  if not working_bufnr then
+    return
+  end
+  local region = M.match_hunk_to_conflict(hunk, working_bufnr)
+  if not region then
+    vim.notify('[diffs.nvim]: hunk does not correspond to a conflict region', vim.log.levels.INFO)
+    return
+  end
+  local lines = vim.api.nvim_buf_get_lines(working_bufnr, region.ours_start, region.ours_end, false)
+  conflict.replace_region(working_bufnr, region, lines)
+  conflict.refresh(working_bufnr, config)
+  mark_resolved(bufnr, hunk.index)
+  add_resolved_virtual_text(bufnr, hunk)
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_theirs(bufnr, config)
+  local hunk = M.find_hunk_at_cursor(bufnr)
+  if not hunk then
+    return
+  end
+  if M.is_resolved(bufnr, hunk.index) then
+    vim.notify('[diffs.nvim]: hunk already resolved', vim.log.levels.INFO)
+    return
+  end
+  local working_bufnr = M.get_or_load_working_buf(bufnr)
+  if not working_bufnr then
+    return
+  end
+  local region = M.match_hunk_to_conflict(hunk, working_bufnr)
+  if not region then
+    vim.notify('[diffs.nvim]: hunk does not correspond to a conflict region', vim.log.levels.INFO)
+    return
+  end
+  local lines =
+    vim.api.nvim_buf_get_lines(working_bufnr, region.theirs_start, region.theirs_end, false)
+  conflict.replace_region(working_bufnr, region, lines)
+  conflict.refresh(working_bufnr, config)
+  mark_resolved(bufnr, hunk.index)
+  add_resolved_virtual_text(bufnr, hunk)
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_both(bufnr, config)
+  local hunk = M.find_hunk_at_cursor(bufnr)
+  if not hunk then
+    return
+  end
+  if M.is_resolved(bufnr, hunk.index) then
+    vim.notify('[diffs.nvim]: hunk already resolved', vim.log.levels.INFO)
+    return
+  end
+  local working_bufnr = M.get_or_load_working_buf(bufnr)
+  if not working_bufnr then
+    return
+  end
+  local region = M.match_hunk_to_conflict(hunk, working_bufnr)
+  if not region then
+    vim.notify('[diffs.nvim]: hunk does not correspond to a conflict region', vim.log.levels.INFO)
+    return
+  end
+  local ours = vim.api.nvim_buf_get_lines(working_bufnr, region.ours_start, region.ours_end, false)
+  local theirs =
+    vim.api.nvim_buf_get_lines(working_bufnr, region.theirs_start, region.theirs_end, false)
+  local combined = {}
+  for _, l in ipairs(ours) do
+    table.insert(combined, l)
+  end
+  for _, l in ipairs(theirs) do
+    table.insert(combined, l)
+  end
+  conflict.replace_region(working_bufnr, region, combined)
+  conflict.refresh(working_bufnr, config)
+  mark_resolved(bufnr, hunk.index)
+  add_resolved_virtual_text(bufnr, hunk)
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.resolve_none(bufnr, config)
+  local hunk = M.find_hunk_at_cursor(bufnr)
+  if not hunk then
+    return
+  end
+  if M.is_resolved(bufnr, hunk.index) then
+    vim.notify('[diffs.nvim]: hunk already resolved', vim.log.levels.INFO)
+    return
+  end
+  local working_bufnr = M.get_or_load_working_buf(bufnr)
+  if not working_bufnr then
+    return
+  end
+  local region = M.match_hunk_to_conflict(hunk, working_bufnr)
+  if not region then
+    vim.notify('[diffs.nvim]: hunk does not correspond to a conflict region', vim.log.levels.INFO)
+    return
+  end
+  conflict.replace_region(working_bufnr, region, {})
+  conflict.refresh(working_bufnr, config)
+  mark_resolved(bufnr, hunk.index)
+  add_resolved_virtual_text(bufnr, hunk)
+end
+
+---@param bufnr integer
+function M.goto_next(bufnr)
+  local hunks = M.parse_hunks(bufnr)
+  if #hunks == 0 then
+    return
+  end
+
+  local working_bufnr = M.get_or_load_working_buf(bufnr)
+  if not working_bufnr then
+    return
+  end
+
+  local cursor_line = vim.api.nvim_win_get_cursor(0)[1] - 1
+
+  local candidates = {}
+  for _, hunk in ipairs(hunks) do
+    if not M.is_resolved(bufnr, hunk.index) then
+      if M.match_hunk_to_conflict(hunk, working_bufnr) then
+        table.insert(candidates, hunk)
+      end
+    end
+  end
+
+  if #candidates == 0 then
+    return
+  end
+
+  for _, hunk in ipairs(candidates) do
+    if hunk.start_line > cursor_line then
+      vim.api.nvim_win_set_cursor(0, { hunk.start_line + 1, 0 })
+      return
+    end
+  end
+
+  vim.notify('[diffs.nvim]: wrapped to first hunk', vim.log.levels.INFO)
+  vim.api.nvim_win_set_cursor(0, { candidates[1].start_line + 1, 0 })
+end
+
+---@param bufnr integer
+function M.goto_prev(bufnr)
+  local hunks = M.parse_hunks(bufnr)
+  if #hunks == 0 then
+    return
+  end
+
+  local working_bufnr = M.get_or_load_working_buf(bufnr)
+  if not working_bufnr then
+    return
+  end
+
+  local cursor_line = vim.api.nvim_win_get_cursor(0)[1] - 1
+
+  local candidates = {}
+  for _, hunk in ipairs(hunks) do
+    if not M.is_resolved(bufnr, hunk.index) then
+      if M.match_hunk_to_conflict(hunk, working_bufnr) then
+        table.insert(candidates, hunk)
+      end
+    end
+  end
+
+  if #candidates == 0 then
+    return
+  end
+
+  for i = #candidates, 1, -1 do
+    if candidates[i].start_line < cursor_line then
+      vim.api.nvim_win_set_cursor(0, { candidates[i].start_line + 1, 0 })
+      return
+    end
+  end
+
+  vim.notify('[diffs.nvim]: wrapped to last hunk', vim.log.levels.INFO)
+  vim.api.nvim_win_set_cursor(0, { candidates[#candidates].start_line + 1, 0 })
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+local function apply_hunk_hints(bufnr, config)
+  if not config.show_virtual_text then
+    return
+  end
+
+  local hunks = M.parse_hunks(bufnr)
+  for _, hunk in ipairs(hunks) do
+    if M.is_resolved(bufnr, hunk.index) then
+      add_resolved_virtual_text(bufnr, hunk)
+    else
+      local parts = {}
+      local actions = {
+        { 'current', config.keymaps.ours },
+        { 'incoming', config.keymaps.theirs },
+        { 'both', config.keymaps.both },
+        { 'none', config.keymaps.none },
+      }
+      for _, action in ipairs(actions) do
+        if action[2] then
+          if #parts > 0 then
+            table.insert(parts, { ' | ', 'Comment' })
+          end
+          table.insert(parts, { ('%s: %s'):format(action[2], action[1]), 'Comment' })
+        end
+      end
+      if #parts > 0 then
+        pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, hunk.start_line, 0, {
+          virt_text = parts,
+          virt_text_pos = 'eol',
+        })
+      end
+    end
+  end
+end
+
+---@param bufnr integer
+---@param config diffs.ConflictConfig
+function M.setup_keymaps(bufnr, config)
+  resolved_hunks[bufnr] = nil
+  vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
+
+  local km = config.keymaps
+
+  local maps = {
+    { km.ours, '<Plug>(diffs-merge-ours)' },
+    { km.theirs, '<Plug>(diffs-merge-theirs)' },
+    { km.both, '<Plug>(diffs-merge-both)' },
+    { km.none, '<Plug>(diffs-merge-none)' },
+    { km.next, '<Plug>(diffs-merge-next)' },
+    { km.prev, '<Plug>(diffs-merge-prev)' },
+  }
+
+  for _, map in ipairs(maps) do
+    if map[1] then
+      vim.keymap.set('n', map[1], map[2], { buffer = bufnr })
+    end
+  end
+
+  apply_hunk_hints(bufnr, config)
+
+  vim.api.nvim_create_autocmd('BufWipeout', {
+    buffer = bufnr,
+    callback = function()
+      resolved_hunks[bufnr] = nil
+    end,
+  })
+end
+
+---@return integer
+function M.get_namespace()
+  return ns
+end
+
+return M

lua/diffs/parser.lua

@@ -12,12 +12,19 @@
 ---@field file_old_count integer?
 ---@field file_new_start integer?
 ---@field file_new_count integer?
+---@field prefix_width integer
+---@field quote_width integer
 ---@field repo_root string?
+---@field context_before string[]?
+---@field context_after string[]?
 
 local M = {}
 
 local dbg = require('diffs.log').dbg
 
+---@type table<string, {ft: string?, lang: string?}>
+local ft_lang_cache = {}
+
 ---@param filepath string
 ---@param n integer
 ---@return string[]?
@@ -56,6 +63,15 @@ local function get_ft_from_filename(filename, repo_root)
   end
 
   local ft = vim.filetype.match({ filename = filename })
+  if not ft and vim.fn.did_filetype() ~= 0 then
+    dbg('retrying filetype match for %s (clearing did_filetype)', filename)
+    local saved = rawget(vim.fn, 'did_filetype')
+    rawset(vim.fn, 'did_filetype', function()
+      return 0
+    end)
+    ft = vim.filetype.match({ filename = filename })
+    rawset(vim.fn, 'did_filetype', saved)
+  end
   if ft then
     dbg('filetype from filename: %s', ft)
     return ft
@@ -106,7 +122,14 @@ local function get_repo_root(bufnr)
     return vim.fn.fnamemodify(git_dir, ':h')
   end
 
-  return nil
+  local ok3, neogit_git_dir = pcall(vim.api.nvim_buf_get_var, bufnr, 'neogit_git_dir')
+  if ok3 and neogit_git_dir then
+    return vim.fn.fnamemodify(neogit_git_dir, ':h')
+  end
+
+  local cwd = vim.fn.getcwd()
+  local git = require('diffs.git')
+  return git.get_repo_root(cwd .. '/.')
 end
 
 ---@param bufnr integer
@@ -114,6 +137,18 @@ end
 function M.parse_buffer(bufnr)
   local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
   local repo_root = get_repo_root(bufnr)
+
+  local quote_prefix = nil
+  local quote_width = 0
+  for _, l in ipairs(lines) do
+    local qp = l:match('^(>+ )diff %-%-') or l:match('^(>+ )@@ %-')
+    if qp then
+      quote_prefix = qp
+      quote_width = #qp
+      break
+    end
+  end
+
   ---@type diffs.Hunk[]
   local hunks = {}
 
@@ -133,6 +168,8 @@ function M.parse_buffer(bufnr)
   local hunk_lines = {}
   ---@type integer?
   local hunk_count = nil
+  ---@type integer
+  local hunk_prefix_width = 1
   ---@type integer?
   local header_start = nil
   ---@type string[]
@@ -145,6 +182,11 @@ function M.parse_buffer(bufnr)
   local file_new_start = nil
   ---@type integer?
   local file_new_count = nil
+  ---@type integer?
+  local old_remaining = nil
+  ---@type integer?
+  local new_remaining = nil
+  local current_quote_width = 0
 
   local function flush_hunk()
     if hunk_start and #hunk_lines > 0 then
@@ -156,6 +198,8 @@ function M.parse_buffer(bufnr)
         header_context = hunk_header_context,
         header_context_col = hunk_header_context_col,
         lines = hunk_lines,
+        prefix_width = hunk_prefix_width,
+        quote_width = current_quote_width,
         file_old_start = file_old_start,
         file_old_count = file_old_count,
         file_new_start = file_new_start,
@@ -176,51 +220,121 @@ function M.parse_buffer(bufnr)
     file_old_count = nil
     file_new_start = nil
     file_new_count = nil
+    old_remaining = nil
+    new_remaining = nil
   end
 
   for i, line in ipairs(lines) do
-    local filename = line:match('^[MADRC%?!]%s+(.+)$') or line:match('^diff %-%-git a/.+ b/(.+)$')
+    local logical = line
+    if quote_prefix then
+      if line:sub(1, quote_width) == quote_prefix then
+        logical = line:sub(quote_width + 1)
+      elseif line:match('^>+$') then
+        logical = ''
+      end
+    end
+
+    local diff_git_file = logical:match('^diff %-%-git a/.+ b/(.+)$')
+      or logical:match('^diff %-%-combined (.+)$')
+      or logical:match('^diff %-%-cc (.+)$')
+    local neogit_file = logical:match('^modified%s+(.+)$')
+      or (not logical:match('^new file mode') and logical:match('^new file%s+(.+)$'))
+      or (not logical:match('^deleted file mode') and logical:match('^deleted%s+(.+)$'))
+      or logical:match('^renamed%s+(.+)$')
+      or logical:match('^copied%s+(.+)$')
+    local bare_file = not hunk_start and logical:match('^([^%s]+%.[^%s]+)$')
+    local filename = logical:match('^[MADRCU%?!]%s+(.+)$')
+      or diff_git_file
+      or neogit_file
+      or bare_file
     if filename then
       flush_hunk()
       current_filename = filename
-      current_ft = get_ft_from_filename(filename, repo_root)
-      current_lang = current_ft and get_lang_from_ft(current_ft) or nil
+      current_quote_width = (logical ~= line) and quote_width or 0
+      local cache_key = (repo_root or '') .. '\0' .. filename
+      local cached = ft_lang_cache[cache_key]
+      if cached then
+        current_ft = cached.ft
+        current_lang = cached.lang
+      else
+        current_ft = get_ft_from_filename(filename, repo_root)
+        current_lang = current_ft and get_lang_from_ft(current_ft) or nil
+        if current_ft or vim.fn.did_filetype() == 0 then
+          ft_lang_cache[cache_key] = { ft = current_ft, lang = current_lang }
+        end
+      end
       if current_lang then
         dbg('file: %s -> lang: %s', filename, current_lang)
       elseif current_ft then
         dbg('file: %s -> ft: %s (no ts parser)', filename, current_ft)
       end
       hunk_count = 0
+      hunk_prefix_width = 1
       header_start = i
       header_lines = {}
-    elseif line:match('^@@.-@@') then
+    elseif logical:match('^@@+') then
       flush_hunk()
       hunk_start = i
-      local hs, hc, hs2, hc2 = line:match('^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@')
-      if hs then
-        file_old_start = tonumber(hs)
-        file_old_count = tonumber(hc) or 1
-        file_new_start = tonumber(hs2)
-        file_new_count = tonumber(hc2) or 1
+      local at_prefix = logical:match('^(@@+)')
+      hunk_prefix_width = #at_prefix - 1
+      if #at_prefix == 2 then
+        local hs, hc, hs2, hc2 = logical:match('^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@')
+        if hs then
+          file_old_start = tonumber(hs)
+          file_old_count = tonumber(hc) or 1
+          file_new_start = tonumber(hs2)
+          file_new_count = tonumber(hc2) or 1
+          old_remaining = file_old_count
+          new_remaining = file_new_count
+        end
+      else
+        local hs, hc = logical:match('%-(%d+),?(%d*)')
+        if hs then
+          file_old_start = tonumber(hs)
+          file_old_count = tonumber(hc) or 1
+          old_remaining = file_old_count
+        end
+        local hs2, hc2 = logical:match('%+(%d+),?(%d*) @@')
+        if hs2 then
+          file_new_start = tonumber(hs2)
+          file_new_count = tonumber(hc2) or 1
+          new_remaining = file_new_count
+        end
       end
-      local prefix, context = line:match('^(@@.-@@%s*)(.*)')
+      local at_end, context = logical:match('^(@@+.-@@+%s*)(.*)')
       if context and context ~= '' then
         hunk_header_context = context
-        hunk_header_context_col = #prefix
+        hunk_header_context_col = #at_end + current_quote_width
       end
       if hunk_count then
         hunk_count = hunk_count + 1
       end
     elseif hunk_start then
-      local prefix = line:sub(1, 1)
+      local prefix = logical:sub(1, 1)
       if prefix == ' ' or prefix == '+' or prefix == '-' then
-        table.insert(hunk_lines, line)
+        table.insert(hunk_lines, logical)
+        if old_remaining and (prefix == ' ' or prefix == '-') then
+          old_remaining = old_remaining - 1
+        end
+        if new_remaining and (prefix == ' ' or prefix == '+') then
+          new_remaining = new_remaining - 1
+        end
       elseif
-        line == ''
-        or line:match('^[MADRC%?!]%s+')
-        or line:match('^diff ')
-        or line:match('^index ')
-        or line:match('^Binary ')
+        logical == ''
+        and old_remaining
+        and old_remaining > 0
+        and new_remaining
+        and new_remaining > 0
+      then
+        table.insert(hunk_lines, string.rep(' ', hunk_prefix_width))
+        old_remaining = old_remaining - 1
+        new_remaining = new_remaining - 1
+      elseif
+        logical == ''
+        or logical:match('^[MADRC%?!]%s+')
+        or logical:match('^diff ')
+        or logical:match('^index ')
+        or logical:match('^Binary ')
       then
         flush_hunk()
         current_filename = nil
@@ -230,7 +344,7 @@ function M.parse_buffer(bufnr)
       end
     end
     if header_start and not hunk_start then
-      table.insert(header_lines, line)
+      table.insert(header_lines, logical)
     end
   end
 
@@ -239,4 +353,10 @@ function M.parse_buffer(bufnr)
   return hunks
 end
 
+M.get_lang_from_ft = get_lang_from_ft
+
+M._test = {
+  ft_lang_cache = ft_lang_cache,
+}
+
 return M

minimal_init.lua

@@ -0,0 +1,61 @@
+vim.cmd([[set runtimepath=$VIMRUNTIME]])
+vim.o.background = 'dark'
+vim.o.number = true
+vim.o.relativenumber = true
+
+local root = vim.fn.fnamemodify('/tmp/diffs-harivansh-repro', ':p')
+vim.opt.packpath = { root }
+vim.env.XDG_CONFIG_HOME = root
+vim.env.XDG_DATA_HOME = root
+vim.env.XDG_STATE_HOME = root
+vim.env.XDG_CACHE_HOME = root
+
+vim.opt.rtp:prepend(vim.fn.expand('~/dev/diffs.nvim'))
+
+local lazypath = root .. '/lazy.nvim'
+if not vim.uv.fs_stat(lazypath) then
+  vim.fn.system({
+    'git',
+    'clone',
+    '--filter=blob:none',
+    '--branch=stable',
+    'https://github.com/folke/lazy.nvim.git',
+    lazypath,
+  })
+end
+vim.opt.rtp:prepend(lazypath)
+
+require('lazy').setup({
+  {
+    dir = vim.fn.expand('~/dev/midnight.nvim'),
+    lazy = false,
+    priority = 1000,
+    config = function()
+      vim.cmd.colorscheme('midnight')
+    end,
+  },
+  { 'tpope/vim-fugitive' },
+  {
+    dir = vim.fn.expand('~/dev/diffs.nvim'),
+    init = function()
+      vim.g.diffs = {
+        integrations = {
+          fugitive = {
+            enabled = true,
+            horizontal = false,
+            vertical = false,
+          },
+        },
+        hide_prefix = false,
+        highlights = {
+          gutter = true,
+          intra = { enabled = true },
+          overrides = {
+            DiffsAdd = { bg = '#ff0000' },
+            DiffsDelete = { bg = '#0000ff' },
+          },
+        },
+      }
+    end,
+  },
+}, { root = root .. '/plugins' })

plugin/diffs.lua

@@ -5,12 +5,50 @@ vim.g.loaded_diffs = 1
 
 require('diffs.commands').setup()
 
+local function get_raw_integration(key)
+  local user = vim.g.diffs or {}
+  local intg = user.integrations or {}
+  local v = intg[key]
+  if v ~= nil then
+    return v
+  end
+  return user[key]
+end
+
+local gs_cfg = get_raw_integration('gitsigns')
+if gs_cfg == true or type(gs_cfg) == 'table' then
+  if not require('diffs.gitsigns').setup() then
+    vim.api.nvim_create_autocmd('User', {
+      pattern = 'GitAttach',
+      once = true,
+      callback = function()
+        require('diffs.gitsigns').setup()
+      end,
+    })
+  end
+end
+
+local tel_cfg = get_raw_integration('telescope')
+if tel_cfg == true or type(tel_cfg) == 'table' then
+  vim.api.nvim_create_autocmd('User', {
+    pattern = 'TelescopePreviewerLoaded',
+    callback = function()
+      require('diffs').attach(vim.api.nvim_get_current_buf())
+    end,
+  })
+end
+
 vim.api.nvim_create_autocmd('FileType', {
-  pattern = { 'fugitive', 'git' },
+  pattern = require('diffs').compute_filetypes(vim.g.diffs or {}),
   callback = function(args)
     local diffs = require('diffs')
-    if args.match == 'git' and not diffs.is_fugitive_buffer(args.buf) then
-      return
+    if args.match == 'git' then
+      local is_fugitive = diffs.get_fugitive_config() and diffs.is_fugitive_buffer(args.buf)
+      local is_committia = diffs.get_committia_config()
+        and vim.api.nvim_buf_get_name(args.buf):match('__committia_diff__$')
+      if not is_fugitive and not is_committia then
+        return
+      end
     end
     diffs.attach(args.buf)
 
@@ -57,3 +95,53 @@ end, { desc = 'Unified diff (horizontal)' })
 vim.keymap.set('n', '<Plug>(diffs-gvdiff)', function()
   cmds.gdiff(nil, true)
 end, { desc = 'Unified diff (vertical)' })
+
+local function conflict_action(fn)
+  local bufnr = vim.api.nvim_get_current_buf()
+  local config = require('diffs').get_conflict_config()
+  fn(bufnr, config)
+end
+
+vim.keymap.set('n', '<Plug>(diffs-conflict-ours)', function()
+  conflict_action(require('diffs.conflict').resolve_ours)
+end, { desc = 'Accept current (ours) change' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-theirs)', function()
+  conflict_action(require('diffs.conflict').resolve_theirs)
+end, { desc = 'Accept incoming (theirs) change' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-both)', function()
+  conflict_action(require('diffs.conflict').resolve_both)
+end, { desc = 'Accept both changes' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-none)', function()
+  conflict_action(require('diffs.conflict').resolve_none)
+end, { desc = 'Reject both changes' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-next)', function()
+  require('diffs.conflict').goto_next(vim.api.nvim_get_current_buf())
+end, { desc = 'Jump to next conflict' })
+vim.keymap.set('n', '<Plug>(diffs-conflict-prev)', function()
+  require('diffs.conflict').goto_prev(vim.api.nvim_get_current_buf())
+end, { desc = 'Jump to previous conflict' })
+
+local function merge_action(fn)
+  local bufnr = vim.api.nvim_get_current_buf()
+  local config = require('diffs').get_conflict_config()
+  fn(bufnr, config)
+end
+
+vim.keymap.set('n', '<Plug>(diffs-merge-ours)', function()
+  merge_action(require('diffs.merge').resolve_ours)
+end, { desc = 'Accept ours in merge diff' })
+vim.keymap.set('n', '<Plug>(diffs-merge-theirs)', function()
+  merge_action(require('diffs.merge').resolve_theirs)
+end, { desc = 'Accept theirs in merge diff' })
+vim.keymap.set('n', '<Plug>(diffs-merge-both)', function()
+  merge_action(require('diffs.merge').resolve_both)
+end, { desc = 'Accept both in merge diff' })
+vim.keymap.set('n', '<Plug>(diffs-merge-none)', function()
+  merge_action(require('diffs.merge').resolve_none)
+end, { desc = 'Reject both in merge diff' })
+vim.keymap.set('n', '<Plug>(diffs-merge-next)', function()
+  require('diffs.merge').goto_next(vim.api.nvim_get_current_buf())
+end, { desc = 'Jump to next conflict hunk' })
+vim.keymap.set('n', '<Plug>(diffs-merge-prev)', function()
+  require('diffs.merge').goto_prev(vim.api.nvim_get_current_buf())
+end, { desc = 'Jump to previous conflict hunk' })

scripts/ci.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+set -eu
+
+nix develop --command stylua --check .
+git ls-files '*.lua' | xargs nix develop --command selene --display-style quiet
+nix develop --command prettier --check .
+nix fmt
+git diff --exit-code -- '*.nix'
+nix develop --command lua-language-server --check . --checklevel=Warning
+nix develop --command busted

selene.toml

@@ -1 +1,4 @@
 std = 'vim'
+
+[lints]
+bad_string_escape = 'allow'

spec/commands_spec.lua

@@ -40,6 +40,78 @@ describe('commands', function()
     end)
   end)
 
+  describe('filter_combined_diffs', function()
+    it('strips diff --cc entries entirely', function()
+      local lines = {
+        'diff --cc main.lua',
+        'index d13ab94,b113aee..0000000',
+        '--- a/main.lua',
+        '+++ b/main.lua',
+        '@@@ -1,7 -1,7 +1,11 @@@',
+        '  local M = {}',
+        '++<<<<<<< HEAD',
+        ' +  return 1',
+        '++=======',
+        '+   return 2',
+        '++>>>>>>> theirs',
+        '  end',
+      }
+      local result = commands.filter_combined_diffs(lines)
+      assert.are.equal(0, #result)
+    end)
+
+    it('preserves diff --git entries', function()
+      local lines = {
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,3 +1,3 @@',
+        ' local M = {}',
+        '-local x = 1',
+        '+local x = 2',
+        ' return M',
+      }
+      local result = commands.filter_combined_diffs(lines)
+      assert.are.equal(8, #result)
+      assert.are.same(lines, result)
+    end)
+
+    it('strips combined but keeps unified in mixed output', function()
+      local lines = {
+        'diff --cc conflict.lua',
+        'index aaa,bbb..000',
+        '@@@ -1,1 -1,1 +1,5 @@@',
+        '++<<<<<<< HEAD',
+        'diff --git a/clean.lua b/clean.lua',
+        '--- a/clean.lua',
+        '+++ b/clean.lua',
+        '@@ -1,1 +1,1 @@',
+        '-old',
+        '+new',
+      }
+      local result = commands.filter_combined_diffs(lines)
+      assert.are.equal(6, #result)
+      assert.are.equal('diff --git a/clean.lua b/clean.lua', result[1])
+      assert.are.equal('+new', result[6])
+    end)
+
+    it('returns empty for empty input', function()
+      local result = commands.filter_combined_diffs({})
+      assert.are.equal(0, #result)
+    end)
+
+    it('returns empty when all entries are combined', function()
+      local lines = {
+        'diff --cc a.lua',
+        'some content',
+        'diff --cc b.lua',
+        'more content',
+      }
+      local result = commands.filter_combined_diffs(lines)
+      assert.are.equal(0, #result)
+    end)
+  end)
+
   describe('find_hunk_line', function()
     it('finds matching @@ header and returns target line', function()
       local diff_lines = {

spec/conflict_spec.lua

@@ -6,13 +6,14 @@ local function default_config(overrides)
     enabled = true,
     disable_diagnostics = false,
     show_virtual_text = true,
+    show_actions = false,
     keymaps = {
       ours = 'doo',
       theirs = 'dot',
       both = 'dob',
       none = 'don',
-      next = ']x',
-      prev = '[x',
+      next = ']c',
+      prev = '[c',
     },
   }
   if overrides then
@@ -234,29 +235,6 @@ describe('conflict', function()
       helpers.delete_buffer(bufnr)
     end)
 
-    it('does not apply virtual text when disabled', function()
-      local bufnr = create_file_buffer({
-        '<<<<<<< HEAD',
-        'local x = 1',
-        '=======',
-        'local x = 2',
-        '>>>>>>> feature',
-      })
-
-      conflict.attach(bufnr, default_config({ show_virtual_text = false }))
-
-      local extmarks = get_extmarks(bufnr)
-      local virt_text_count = 0
-      for _, mark in ipairs(extmarks) do
-        if mark[4] and mark[4].virt_text then
-          virt_text_count = virt_text_count + 1
-        end
-      end
-      assert.are.equal(0, virt_text_count)
-
-      helpers.delete_buffer(bufnr)
-    end)
-
     it('applies number_hl_group to content lines', function()
       local bufnr = create_file_buffer({
         '<<<<<<< HEAD',
@@ -531,6 +509,33 @@ describe('conflict', function()
       helpers.delete_buffer(bufnr)
     end)
 
+    it('goto_next notifies on wrap-around', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      local notified = false
+      local orig_notify = vim.notify
+      vim.notify = function(msg)
+        if msg:match('wrapped to first conflict') then
+          notified = true
+        end
+      end
+
+      conflict.goto_next(bufnr)
+      vim.notify = orig_notify
+
+      assert.is_true(notified)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
     it('goto_prev jumps to previous conflict', function()
       local bufnr = create_file_buffer({
         '<<<<<<< HEAD',
@@ -575,6 +580,33 @@ describe('conflict', function()
       helpers.delete_buffer(bufnr)
     end)
 
+    it('goto_prev notifies on wrap-around', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'a',
+        '=======',
+        'b',
+        '>>>>>>> feat',
+      })
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      local notified = false
+      local orig_notify = vim.notify
+      vim.notify = function(msg)
+        if msg:match('wrapped to last conflict') then
+          notified = true
+        end
+      end
+
+      conflict.goto_prev(bufnr)
+      vim.notify = orig_notify
+
+      assert.is_true(notified)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
     it('goto_next does nothing with no conflicts', function()
       local bufnr = create_file_buffer({ 'normal line' })
       vim.api.nvim_set_current_buf(bufnr)
@@ -685,4 +717,158 @@ describe('conflict', function()
       helpers.delete_buffer(bufnr)
     end)
   end)
+
+  describe('virtual text formatting', function()
+    after_each(function()
+      conflict.detach(vim.api.nvim_get_current_buf())
+    end)
+
+    it('default labels show current and incoming without keymaps', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config())
+
+      local extmarks = get_extmarks(bufnr)
+      local labels = {}
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          table.insert(labels, mark[4].virt_text[1][1])
+        end
+      end
+      assert.are.equal(2, #labels)
+      assert.are.equal(' (current)', labels[1])
+      assert.are.equal(' (incoming)', labels[2])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('uses custom format_virtual_text function', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(
+        bufnr,
+        default_config({
+          format_virtual_text = function(side)
+            return side == 'ours' and 'OURS' or 'THEIRS'
+          end,
+        })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      local labels = {}
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          table.insert(labels, mark[4].virt_text[1][1])
+        end
+      end
+      assert.are.equal(2, #labels)
+      assert.are.equal(' (OURS)', labels[1])
+      assert.are.equal(' (THEIRS)', labels[2])
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('hides label when format_virtual_text returns nil', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(
+        bufnr,
+        default_config({
+          format_virtual_text = function()
+            return nil
+          end,
+        })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      local virt_text_count = 0
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          virt_text_count = virt_text_count + 1
+        end
+      end
+      assert.are.equal(0, virt_text_count)
+
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('action lines', function()
+    after_each(function()
+      conflict.detach(vim.api.nvim_get_current_buf())
+    end)
+
+    it('adds virt_lines when show_actions is true', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(bufnr, default_config({ show_actions = true }))
+
+      local extmarks = get_extmarks(bufnr)
+      local virt_lines_count = 0
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_lines then
+          virt_lines_count = virt_lines_count + 1
+        end
+      end
+      assert.are.equal(1, virt_lines_count)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('omits disabled keymaps from action line', function()
+      local bufnr = create_file_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      })
+
+      conflict.attach(
+        bufnr,
+        default_config({ show_actions = true, keymaps = { both = false, none = false } })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_lines then
+          local line = mark[4].virt_lines[1]
+          local text = ''
+          for _, chunk in ipairs(line) do
+            text = text .. chunk[1]
+          end
+          assert.is_truthy(text:find('Current'))
+          assert.is_truthy(text:find('Incoming'))
+          assert.is_falsy(text:find('Both'))
+          assert.is_falsy(text:find('None'))
+        end
+      end
+
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
 end)

spec/context_spec.lua

@@ -0,0 +1,382 @@
+require('spec.helpers')
+local diffs = require('diffs')
+local highlight = require('diffs.highlight')
+local compute_hunk_context = diffs._test.compute_hunk_context
+
+describe('context', function()
+  describe('compute_hunk_context', function()
+    local tmpdir
+
+    before_each(function()
+      tmpdir = vim.fn.tempname()
+      vim.fn.mkdir(tmpdir, 'p')
+    end)
+
+    after_each(function()
+      vim.fn.delete(tmpdir, 'rf')
+    end)
+
+    local function write_file(filename, lines)
+      local path = vim.fs.joinpath(tmpdir, filename)
+      local dir = vim.fn.fnamemodify(path, ':h')
+      if vim.fn.isdirectory(dir) == 0 then
+        vim.fn.mkdir(dir, 'p')
+      end
+      local f = io.open(path, 'w')
+      f:write(table.concat(lines, '\n') .. '\n')
+      f:close()
+    end
+
+    local function make_hunk(filename, opts)
+      return {
+        filename = filename,
+        ft = 'lua',
+        lang = 'lua',
+        start_line = opts.start_line or 1,
+        lines = opts.lines,
+        prefix_width = opts.prefix_width or 1,
+        quote_width = 0,
+        repo_root = tmpdir,
+        file_new_start = opts.file_new_start,
+        file_new_count = opts.file_new_count,
+      }
+    end
+
+    it('reads context_before from file lines preceding the hunk', function()
+      write_file('a.lua', {
+        'local M = {}',
+        'function M.foo()',
+        '  local x = 1',
+        '  local y = 2',
+        'end',
+        'return M',
+      })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = 3,
+          file_new_count = 3,
+          lines = { ' local x = 1', '+local new = true', ' local y = 2' },
+        }),
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.same({ 'local M = {}', 'function M.foo()' }, hunks[1].context_before)
+    end)
+
+    it('reads context_after from file lines following the hunk', function()
+      write_file('a.lua', {
+        'local M = {}',
+        'function M.foo()',
+        '  local x = 1',
+        'end',
+        'return M',
+      })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = 2,
+          file_new_count = 2,
+          lines = { ' function M.foo()', '+  local x = 1' },
+        }),
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.same({ 'end', 'return M' }, hunks[1].context_after)
+    end)
+
+    it('caps context_before to max_lines', function()
+      write_file('a.lua', {
+        'line1',
+        'line2',
+        'line3',
+        'line4',
+        'line5',
+        'target',
+      })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = 6,
+          file_new_count = 1,
+          lines = { '+target' },
+        }),
+      }
+      compute_hunk_context(hunks, 2)
+
+      assert.same({ 'line4', 'line5' }, hunks[1].context_before)
+    end)
+
+    it('caps context_after to max_lines', function()
+      write_file('a.lua', {
+        'target',
+        'after1',
+        'after2',
+        'after3',
+        'after4',
+      })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = 1,
+          file_new_count = 1,
+          lines = { '+target' },
+        }),
+      }
+      compute_hunk_context(hunks, 2)
+
+      assert.same({ 'after1', 'after2' }, hunks[1].context_after)
+    end)
+
+    it('skips hunks without file_new_start', function()
+      write_file('a.lua', { 'line1', 'line2' })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = nil,
+          file_new_count = nil,
+          lines = { '+something' },
+        }),
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.is_nil(hunks[1].context_before)
+      assert.is_nil(hunks[1].context_after)
+    end)
+
+    it('skips hunks without repo_root', function()
+      local hunks = {
+        {
+          filename = 'a.lua',
+          ft = 'lua',
+          lang = 'lua',
+          start_line = 1,
+          lines = { '+x' },
+          prefix_width = 1,
+          quote_width = 0,
+          repo_root = nil,
+          file_new_start = 1,
+          file_new_count = 1,
+        },
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.is_nil(hunks[1].context_before)
+      assert.is_nil(hunks[1].context_after)
+    end)
+
+    it('skips when file does not exist on disk', function()
+      local hunks = {
+        make_hunk('nonexistent.lua', {
+          file_new_start = 1,
+          file_new_count = 1,
+          lines = { '+x' },
+        }),
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.is_nil(hunks[1].context_before)
+      assert.is_nil(hunks[1].context_after)
+    end)
+
+    it('returns nil context_before for hunk at line 1', function()
+      write_file('a.lua', { 'first', 'second' })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = 1,
+          file_new_count = 1,
+          lines = { '+first' },
+        }),
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.is_nil(hunks[1].context_before)
+    end)
+
+    it('returns nil context_after for hunk at end of file', function()
+      write_file('a.lua', { 'first', 'last' })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = 1,
+          file_new_count = 2,
+          lines = { ' first', '+last' },
+        }),
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.is_nil(hunks[1].context_after)
+    end)
+
+    it('reads file once for multiple hunks in same file', function()
+      write_file('a.lua', {
+        'local M = {}',
+        'function M.foo()',
+        '  return 1',
+        'end',
+        'function M.bar()',
+        '  return 2',
+        'end',
+        'return M',
+      })
+
+      local hunks = {
+        make_hunk('a.lua', {
+          file_new_start = 2,
+          file_new_count = 3,
+          lines = { ' function M.foo()', '+  return 1', ' end' },
+        }),
+        make_hunk('a.lua', {
+          file_new_start = 5,
+          file_new_count = 3,
+          lines = { ' function M.bar()', '+  return 2', ' end' },
+        }),
+      }
+      compute_hunk_context(hunks, 25)
+
+      assert.same({ 'local M = {}' }, hunks[1].context_before)
+      assert.same({ 'function M.bar()', '  return 2', 'end', 'return M' }, hunks[1].context_after)
+      assert.same({
+        'local M = {}',
+        'function M.foo()',
+        '  return 1',
+        'end',
+      }, hunks[2].context_before)
+      assert.same({ 'return M' }, hunks[2].context_after)
+    end)
+  end)
+
+  describe('highlight_treesitter with context', function()
+    local ns
+
+    before_each(function()
+      ns = vim.api.nvim_create_namespace('diffs_context_test')
+      local normal = vim.api.nvim_get_hl(0, { name = 'Normal' })
+      vim.api.nvim_set_hl(0, 'DiffsClear', { fg = normal.fg or 0xc0c0c0 })
+    end)
+
+    local function create_buffer(lines)
+      local bufnr = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+      return bufnr
+    end
+
+    local function delete_buffer(bufnr)
+      if vim.api.nvim_buf_is_valid(bufnr) then
+        vim.api.nvim_buf_delete(bufnr, { force = true })
+      end
+    end
+
+    local function get_extmarks(bufnr)
+      return vim.api.nvim_buf_get_extmarks(bufnr, ns, 0, -1, { details = true })
+    end
+
+    local function default_opts(overrides)
+      local opts = {
+        hide_prefix = false,
+        highlights = {
+          background = false,
+          gutter = false,
+          context = { enabled = true, lines = 25 },
+          treesitter = { enabled = true, max_lines = 500 },
+          vim = { enabled = false, max_lines = 200 },
+          intra = { enabled = false, algorithm = 'default', max_lines = 500 },
+          priorities = { clear = 198, syntax = 199, line_bg = 200, char_bg = 201 },
+        },
+      }
+      if overrides then
+        if overrides.highlights then
+          opts.highlights = vim.tbl_deep_extend('force', opts.highlights, overrides.highlights)
+        end
+      end
+      return opts
+    end
+
+    it('applies extmarks only to hunk lines, not context lines', function()
+      local bufnr = create_buffer({
+        '@@ -1,2 +1,3 @@',
+        ' local x = 1',
+        ' local y = 2',
+        '+local z = 3',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 2,
+        lines = { ' local x = 1', ' local y = 2', '+local z = 3' },
+        prefix_width = 1,
+        quote_width = 0,
+        context_before = { 'local function foo()' },
+        context_after = { 'end' },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      for _, mark in ipairs(extmarks) do
+        local row = mark[2]
+        assert.is_true(row >= 1 and row <= 3, 'extmark row ' .. row .. ' outside hunk range')
+      end
+      assert.is_true(#extmarks > 0)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not pass context when context.enabled = false', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 2,
+        lines = { ' local x = 1', '+local y = 2' },
+        prefix_width = 1,
+        quote_width = 0,
+        context_before = { 'local function foo()' },
+        context_after = { 'end' },
+      }
+
+      local opts_enabled = default_opts({ highlights = { context = { enabled = true } } })
+      highlight.highlight_hunk(bufnr, ns, hunk, opts_enabled)
+      local extmarks_with = get_extmarks(bufnr)
+
+      vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
+
+      local opts_disabled = default_opts({ highlights = { context = { enabled = false } } })
+      highlight.highlight_hunk(bufnr, ns, hunk, opts_disabled)
+      local extmarks_without = get_extmarks(bufnr)
+
+      assert.is_true(#extmarks_with > 0)
+      assert.is_true(#extmarks_without > 0)
+      delete_buffer(bufnr)
+    end)
+
+    it('skips context fields that are nil', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 2,
+        lines = { ' local x = 1', '+local y = 2' },
+        prefix_width = 1,
+        quote_width = 0,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      assert.is_true(#extmarks > 0)
+      delete_buffer(bufnr)
+    end)
+  end)
+end)

spec/decoration_provider_spec.lua

@@ -0,0 +1,329 @@
+require('spec.helpers')
+local diffs = require('diffs')
+
+describe('decoration_provider', function()
+  local function create_buffer(lines)
+    local bufnr = vim.api.nvim_create_buf(false, true)
+    vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines or {})
+    return bufnr
+  end
+
+  local function delete_buffer(bufnr)
+    if vim.api.nvim_buf_is_valid(bufnr) then
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+    end
+  end
+
+  describe('ensure_cache', function()
+    it('populates hunk cache for a buffer with diff content', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        ' local z = 4',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.is_table(entry.hunks)
+      assert.is_true(#entry.hunks > 0)
+      delete_buffer(bufnr)
+    end)
+
+    it('cache tick matches buffer changedtick after attach', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      local tick = vim.api.nvim_buf_get_changedtick(bufnr)
+      assert.are.equal(tick, entry.tick)
+      delete_buffer(bufnr)
+    end)
+
+    it('re-parses and advances tick when buffer content changes', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local tick_before = diffs._test.hunk_cache[bufnr].tick
+      vim.api.nvim_buf_set_lines(bufnr, -1, -1, false, { '+local z = 3' })
+      diffs._test.ensure_cache(bufnr)
+      local tick_after = diffs._test.hunk_cache[bufnr].tick
+      assert.is_true(tick_after > tick_before)
+      delete_buffer(bufnr)
+    end)
+
+    it('skips reparse when fingerprint unchanged but sets pending_clear', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      local original_hunks = entry.hunks
+      entry.pending_clear = false
+
+      local lc = vim.api.nvim_buf_line_count(bufnr)
+      local bc = vim.api.nvim_buf_get_offset(bufnr, lc)
+      entry.line_count = lc
+      entry.byte_count = bc
+      entry.tick = -1
+
+      diffs._test.ensure_cache(bufnr)
+
+      local updated = diffs._test.hunk_cache[bufnr]
+      local current_tick = vim.api.nvim_buf_get_changedtick(bufnr)
+      assert.are.equal(original_hunks, updated.hunks)
+      assert.are.equal(current_tick, updated.tick)
+      assert.is_true(updated.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('does nothing for invalid buffer', function()
+      local bufnr = create_buffer({})
+      diffs.attach(bufnr)
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+      assert.has_no.errors(function()
+        diffs._test.ensure_cache(bufnr)
+      end)
+    end)
+  end)
+
+  describe('pending_clear', function()
+    it('is true after invalidate_cache', function()
+      local bufnr = create_buffer({})
+      diffs.attach(bufnr)
+      diffs._test.invalidate_cache(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_true(entry.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('is true immediately after fresh ensure_cache', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_true(entry.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('clears namespace extmarks when on_buf processes pending_clear', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local ns_id = vim.api.nvim_create_namespace('diffs')
+      vim.api.nvim_buf_set_extmark(bufnr, ns_id, 0, 0, { line_hl_group = 'DiffAdd' })
+      assert.are.equal(1, #vim.api.nvim_buf_get_extmarks(bufnr, ns_id, 0, -1, {}))
+
+      diffs._test.invalidate_cache(bufnr)
+      diffs._test.ensure_cache(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_true(entry.pending_clear)
+
+      diffs._test.process_pending_clear(bufnr)
+
+      entry = diffs._test.hunk_cache[bufnr]
+      assert.is_false(entry.pending_clear)
+      assert.are.same({}, vim.api.nvim_buf_get_extmarks(bufnr, ns_id, 0, -1, {}))
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('BufWipeout cleanup', function()
+    it('removes hunk_cache entry after buffer wipeout', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      assert.is_not_nil(diffs._test.hunk_cache[bufnr])
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+      assert.is_nil(diffs._test.hunk_cache[bufnr])
+    end)
+  end)
+
+  describe('hunk stability', function()
+    it('carries forward highlighted for stable hunks on section expansion', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,2 +1,2 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        '@@ -10,2 +10,3 @@',
+        ' function M.foo()',
+        '+  return true',
+        ' end',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(2, #entry.hunks)
+
+      entry.pending_clear = false
+      entry.highlighted = { [1] = true, [2] = true }
+
+      vim.api.nvim_buf_set_lines(bufnr, 5, 5, false, {
+        '@@ -5,1 +5,2 @@',
+        ' local z = 4',
+        '+local w = 5',
+      })
+      diffs._test.ensure_cache(bufnr)
+
+      local updated = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(3, #updated.hunks)
+      assert.is_true(updated.highlighted[1] == true)
+      assert.is_nil(updated.highlighted[2])
+      assert.is_true(updated.highlighted[3] == true)
+      assert.is_false(updated.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('carries forward highlighted for stable hunks on section collapse', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,2 +1,2 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        '@@ -5,1 +5,2 @@',
+        ' local z = 4',
+        '+local w = 5',
+        '@@ -10,2 +10,3 @@',
+        ' function M.foo()',
+        '+  return true',
+        ' end',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(3, #entry.hunks)
+
+      entry.pending_clear = false
+      entry.highlighted = { [1] = true, [2] = true, [3] = true }
+
+      vim.api.nvim_buf_set_lines(bufnr, 5, 8, false, {})
+      diffs._test.ensure_cache(bufnr)
+
+      local updated = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(2, #updated.hunks)
+      assert.is_true(updated.highlighted[1] == true)
+      assert.is_true(updated.highlighted[2] == true)
+      assert.is_false(updated.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('bypasses carry-forward when pending_clear was true', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,2 +1,2 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        '@@ -10,2 +10,3 @@',
+        ' function M.foo()',
+        '+  return true',
+        ' end',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      entry.highlighted = { [1] = true, [2] = true }
+      entry.pending_clear = true
+
+      vim.api.nvim_buf_set_lines(bufnr, 5, 5, false, {
+        '@@ -5,1 +5,2 @@',
+        ' local z = 4',
+        '+local w = 5',
+      })
+      diffs._test.ensure_cache(bufnr)
+
+      local updated = diffs._test.hunk_cache[bufnr]
+      assert.are.same({}, updated.highlighted)
+      assert.is_true(updated.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not carry forward when all hunks changed', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,2 +1,2 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+
+      entry.pending_clear = false
+      entry.highlighted = { [1] = true }
+
+      vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, {
+        'M other.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local a = 1',
+        '+local b = 2',
+      })
+      diffs._test.ensure_cache(bufnr)
+
+      local updated = diffs._test.hunk_cache[bufnr]
+      assert.is_nil(updated.highlighted[1])
+      assert.is_true(updated.pending_clear)
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('multiple hunks in cache', function()
+    it('stores all parsed hunks for a multi-hunk buffer', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,2 +1,2 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        '@@ -10,2 +10,3 @@',
+        ' function M.foo()',
+        '+  return true',
+        ' end',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.are.equal(2, #entry.hunks)
+      delete_buffer(bufnr)
+    end)
+
+    it('stores empty hunks table for buffer with no diff content', function()
+      local bufnr = create_buffer({
+        'Head: main',
+        'Help: g?',
+        '',
+        'Nothing to see here',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.are.same({}, entry.hunks)
+      delete_buffer(bufnr)
+    end)
+  end)
+end)

spec/email_quote_spec.lua

@@ -0,0 +1,477 @@
+require('spec.helpers')
+local highlight = require('diffs.highlight')
+local parser = require('diffs.parser')
+
+describe('email-quoted diffs', function()
+  local function create_buffer(lines)
+    local bufnr = vim.api.nvim_create_buf(false, true)
+    vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+    return bufnr
+  end
+
+  local function delete_buffer(bufnr)
+    if vim.api.nvim_buf_is_valid(bufnr) then
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+    end
+  end
+
+  describe('parser', function()
+    it('parses a fully email-quoted unified diff', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.py b/foo.py',
+        '> index abc1234..def5678 100644',
+        '> --- a/foo.py',
+        '> +++ b/foo.py',
+        '> @@ -0,0 +1,3 @@',
+        '> +from typing import Annotated, final',
+        '> +',
+        '> +class Foo:',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('foo.py', hunks[1].filename)
+      assert.are.equal(3, #hunks[1].lines)
+      assert.are.equal('+from typing import Annotated, final', hunks[1].lines[1])
+      assert.are.equal(2, hunks[1].quote_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('parses a quoted diff embedded in an email reply', function()
+      local bufnr = create_buffer({
+        'Looks good, one nit:',
+        '',
+        '> diff --git a/foo.py b/foo.py',
+        '> @@ -0,0 +1,3 @@',
+        '> +from typing import Annotated, final',
+        '> +',
+        '> +class Foo:',
+        '',
+        'Maybe rename Foo to Bar?',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('foo.py', hunks[1].filename)
+      assert.are.equal(3, #hunks[1].lines)
+      assert.are.equal(2, hunks[1].quote_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('sets quote_width = 0 on normal (unquoted) diffs', function()
+      local bufnr = create_buffer({
+        'diff --git a/bar.lua b/bar.lua',
+        '@@ -1,2 +1,2 @@',
+        '-old_line',
+        '+new_line',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(0, hunks[1].quote_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('treats bare > lines as empty quoted lines', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.py b/foo.py',
+        '> @@ -1,3 +1,3 @@',
+        '> -old',
+        '>',
+        '> +new',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(3, #hunks[1].lines)
+      assert.are.equal('-old', hunks[1].lines[1])
+      assert.are.equal(' ', hunks[1].lines[2])
+      assert.are.equal('+new', hunks[1].lines[3])
+      delete_buffer(bufnr)
+    end)
+
+    it('handles deeply nested quotes', function()
+      local bufnr = create_buffer({
+        '>> diff --git a/foo.py b/foo.py',
+        '>> @@ -0,0 +1,2 @@',
+        '>> +line1',
+        '>> +line2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(3, hunks[1].quote_width)
+      assert.are.equal('+line1', hunks[1].lines[1])
+      delete_buffer(bufnr)
+    end)
+
+    it('adjusts header_context_col for quote width', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.py b/foo.py',
+        '> @@ -1,2 +1,2 @@ def hello():',
+        '> -old',
+        '> +new',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('def hello():', hunks[1].header_context)
+      assert.are.equal(#'@@ -1,2 +1,2 @@ ' + 2, hunks[1].header_context_col)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not false-positive on prose containing > diff', function()
+      local bufnr = create_buffer({
+        '> diff between approaches is small',
+        '> I think we should go with option A',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(0, #hunks)
+      delete_buffer(bufnr)
+    end)
+
+    it('stores header lines stripped of quote prefix', function()
+      local bufnr = create_buffer({
+        '> diff --git a/foo.lua b/foo.lua',
+        '> index abc1234..def5678 100644',
+        '> --- a/foo.lua',
+        '> +++ b/foo.lua',
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.is_not_nil(hunks[1].header_lines)
+      for _, hline in ipairs(hunks[1].header_lines) do
+        assert.is_nil(hline:match('^> '))
+      end
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('highlight', function()
+    local ns
+
+    before_each(function()
+      ns = vim.api.nvim_create_namespace('diffs_email_test')
+      vim.api.nvim_set_hl(0, 'DiffsClear', { fg = 0xc0c0c0, bg = 0x1e1e1e })
+      vim.api.nvim_set_hl(0, 'DiffsAdd', { bg = 0x1a3a1a })
+      vim.api.nvim_set_hl(0, 'DiffsDelete', { bg = 0x3a1a1a })
+      vim.api.nvim_set_hl(0, 'DiffsConflictMarker', { fg = 0x808080, bold = true })
+    end)
+
+    local function get_extmarks(bufnr)
+      return vim.api.nvim_buf_get_extmarks(bufnr, ns, 0, -1, { details = true })
+    end
+
+    local function default_opts(overrides)
+      local opts = {
+        hide_prefix = false,
+        highlights = {
+          background = true,
+          gutter = false,
+          context = { enabled = false, lines = 0 },
+          treesitter = {
+            enabled = true,
+            max_lines = 500,
+          },
+          vim = {
+            enabled = false,
+            max_lines = 200,
+          },
+          intra = {
+            enabled = false,
+            algorithm = 'default',
+            max_lines = 500,
+          },
+          priorities = {
+            clear = 198,
+            syntax = 199,
+            line_bg = 200,
+            char_bg = 201,
+          },
+        },
+      }
+      if overrides then
+        if overrides.highlights then
+          opts.highlights = vim.tbl_deep_extend('force', opts.highlights, overrides.highlights)
+        end
+        for k, v in pairs(overrides) do
+          if k ~= 'highlights' then
+            opts[k] = v
+          end
+        end
+      end
+      return opts
+    end
+
+    it('applies DiffsClear on email-quoted header lines covering full buffer width', function()
+      local buf_lines = {
+        '> diff --git a/foo.lua b/foo.lua',
+        '> index abc1234..def5678 100644',
+        '> --- a/foo.lua',
+        '> +++ b/foo.lua',
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      }
+      local bufnr = create_buffer(buf_lines)
+
+      local hunk = {
+        filename = 'foo.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 5,
+        lines = { '-old', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+        header_start_line = 1,
+        header_lines = {
+          'diff --git a/foo.lua b/foo.lua',
+          'index abc1234..def5678 100644',
+          '--- a/foo.lua',
+          '+++ b/foo.lua',
+        },
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local header_clears = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group == 'DiffsClear' and mark[2] < 4 then
+          table.insert(header_clears, { row = mark[2], col = mark[3], end_col = d.end_col })
+        end
+      end
+      assert.is_true(#header_clears > 0)
+      for _, c in ipairs(header_clears) do
+        assert.are.equal(0, c.col)
+        local buf_line_len = #buf_lines[c.row + 1]
+        assert.are.equal(buf_line_len, c.end_col)
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('applies body prefix DiffsClear covering [0, pw+qw)', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      })
+
+      local hunk = {
+        filename = 'foo.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { '-old', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local prefix_clears = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group == 'DiffsClear' and d.end_col == 3 and mark[3] == 0 then
+          table.insert(prefix_clears, { row = mark[2] })
+        end
+      end
+      assert.are.equal(2, #prefix_clears)
+
+      delete_buffer(bufnr)
+    end)
+
+    it('clamps body prefix DiffsClear on bare > lines (1-byte buffer line)', function()
+      local bufnr = create_buffer({
+        '> @@ -1,3 +1,3 @@',
+        '> -old',
+        '>',
+        '> +new',
+      })
+
+      local hunk = {
+        filename = 'foo.lua',
+        ft = 'lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { '-old', ' ', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local bare_line_row = 2
+      local bare_clears = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group == 'DiffsClear' and mark[2] == bare_line_row and mark[3] == 0 then
+          table.insert(bare_clears, { end_col = d.end_col })
+        end
+      end
+      assert.are.equal(1, #bare_clears)
+      assert.are.equal(1, bare_clears[1].end_col)
+
+      delete_buffer(bufnr)
+    end)
+
+    it('applies per-char @diff.plus/@diff.minus at ci + qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,1 @@',
+        '> -old',
+        '> +new',
+      })
+
+      local hunk = {
+        filename = 'foo.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { '-old', '+new' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local diff_marks = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and (d.hl_group == '@diff.plus' or d.hl_group == '@diff.minus') then
+          table.insert(
+            diff_marks,
+            { row = mark[2], col = mark[3], end_col = d.end_col, hl = d.hl_group }
+          )
+        end
+      end
+      assert.is_true(#diff_marks >= 2)
+      for _, dm in ipairs(diff_marks) do
+        assert.are.equal(2, dm.col)
+        assert.are.equal(3, dm.end_col)
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('offsets treesitter extmarks by pw + qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,2 @@',
+        '>  local x = 1',
+        '> +local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+
+      local extmarks = get_extmarks(bufnr)
+      local ts_marks = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.hl_group and d.hl_group:match('^@.*%.lua$') then
+          table.insert(ts_marks, { row = mark[2], col = mark[3] })
+        end
+      end
+      assert.is_true(#ts_marks > 0)
+      for _, tm in ipairs(ts_marks) do
+        assert.is_true(tm.col >= 3)
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('offsets intra-line char span extmarks by qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,1 @@',
+        '> -hello world',
+        '> +hello earth',
+      })
+
+      local hunk = {
+        filename = 'test.txt',
+        ft = nil,
+        lang = nil,
+        start_line = 1,
+        lines = { '-hello world', '+hello earth' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(
+        bufnr,
+        ns,
+        hunk,
+        default_opts({
+          highlights = { intra = { enabled = true, algorithm = 'default', max_lines = 500 } },
+        })
+      )
+
+      local extmarks = get_extmarks(bufnr)
+      local char_marks = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and (d.hl_group == 'DiffsAddText' or d.hl_group == 'DiffsDeleteText') then
+          table.insert(char_marks, { row = mark[2], col = mark[3], end_col = d.end_col })
+        end
+      end
+      if #char_marks > 0 then
+        for _, cm in ipairs(char_marks) do
+          assert.is_true(cm.col >= 2)
+        end
+      end
+
+      delete_buffer(bufnr)
+    end)
+
+    it('does not produce duplicate extmarks with syntax_only + qw', function()
+      local bufnr = create_buffer({
+        '> @@ -1,1 +1,2 @@',
+        '>  local x = 1',
+        '> +local y = 2',
+      })
+
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        ft = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2' },
+        prefix_width = 1,
+        quote_width = 2,
+      }
+
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
+      highlight.highlight_hunk(bufnr, ns, hunk, default_opts({ syntax_only = true }))
+
+      local extmarks = get_extmarks(bufnr)
+      local line_bg_count = 0
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.line_hl_group == 'DiffsAdd' then
+          line_bg_count = line_bg_count + 1
+        end
+      end
+      assert.are.equal(1, line_bg_count)
+
+      delete_buffer(bufnr)
+    end)
+  end)
+end)

spec/fugitive_spec.lua

@@ -87,28 +87,6 @@ describe('fugitive', function()
       vim.api.nvim_buf_delete(buf, { force = true })
     end)
 
-    it('parses added file', function()
-      local buf = create_status_buffer({
-        'Staged (1)',
-        'A  newfile.lua',
-      })
-      local filename, section = fugitive.get_file_at_line(buf, 2)
-      assert.equals('newfile.lua', filename)
-      assert.equals('staged', section)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('parses deleted file', function()
-      local buf = create_status_buffer({
-        'Staged (1)',
-        'D  oldfile.lua',
-      })
-      local filename, section = fugitive.get_file_at_line(buf, 2)
-      assert.equals('oldfile.lua', filename)
-      assert.equals('staged', section)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
     it('parses renamed file and returns both names', function()
       local buf = create_status_buffer({
         'Staged (1)',
@@ -157,28 +135,6 @@ describe('fugitive', function()
       vim.api.nvim_buf_delete(buf, { force = true })
     end)
 
-    it('handles renamed file in subdirectory', function()
-      local buf = create_status_buffer({
-        'Staged (1)',
-        'R  src/old.lua -> src/new.lua',
-      })
-      local filename, _, _, old_filename = fugitive.get_file_at_line(buf, 2)
-      assert.equals('src/new.lua', filename)
-      assert.equals('src/old.lua', old_filename)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('handles renamed file moved to different directory', function()
-      local buf = create_status_buffer({
-        'Staged (1)',
-        'R  old/file.lua -> new/file.lua',
-      })
-      local filename, _, _, old_filename = fugitive.get_file_at_line(buf, 2)
-      assert.equals('new/file.lua', filename)
-      assert.equals('old/file.lua', old_filename)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
     it('KNOWN LIMITATION: filename containing arrow parsed incorrectly', function()
       local buf = create_status_buffer({
         'Staged (1)',
@@ -190,77 +146,54 @@ describe('fugitive', function()
       vim.api.nvim_buf_delete(buf, { force = true })
     end)
 
-    it('handles double extensions', function()
+    it('unquotes git-quoted filenames with spaces', function()
+      local buf = create_status_buffer({
+        'Unstaged (1)',
+        'M  "path with spaces/file.lua"',
+      })
+      local filename = fugitive.get_file_at_line(buf, 2)
+      assert.equals('path with spaces/file.lua', filename)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('unquotes escaped quotes in filenames', function()
+      local buf = create_status_buffer({
+        'Unstaged (1)',
+        'M  "file\\"name.lua"',
+      })
+      local filename = fugitive.get_file_at_line(buf, 2)
+      assert.equals('file"name.lua', filename)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('unquotes octal escapes in filenames', function()
+      local buf = create_status_buffer({
+        'Unstaged (1)',
+        'M  "\\303\\251le.lua"',
+      })
+      local filename = fugitive.get_file_at_line(buf, 2)
+      assert.equals('\195\169le.lua', filename)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('passes through unquoted filenames unchanged', function()
+      local buf = create_status_buffer({
+        'Unstaged (1)',
+        'M  normal.lua',
+      })
+      local filename = fugitive.get_file_at_line(buf, 2)
+      assert.equals('normal.lua', filename)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('unquotes renamed files with quotes', function()
       local buf = create_status_buffer({
         'Staged (1)',
-        'M  test.spec.lua',
+        'R100 "old name.lua" -> "new name.lua"',
       })
       local filename, _, _, old_filename = fugitive.get_file_at_line(buf, 2)
-      assert.equals('test.spec.lua', filename)
-      assert.is_nil(old_filename)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('handles hyphenated filenames', function()
-      local buf = create_status_buffer({
-        'Unstaged (1)',
-        'M  my-component-test.lua',
-      })
-      local filename, section = fugitive.get_file_at_line(buf, 2)
-      assert.equals('my-component-test.lua', filename)
-      assert.equals('unstaged', section)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('handles underscores and numbers', function()
-      local buf = create_status_buffer({
-        'Staged (1)',
-        'A  test_file_123.lua',
-      })
-      local filename = fugitive.get_file_at_line(buf, 2)
-      assert.equals('test_file_123.lua', filename)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('handles dotfiles', function()
-      local buf = create_status_buffer({
-        'Unstaged (1)',
-        'M  .gitignore',
-      })
-      local filename = fugitive.get_file_at_line(buf, 2)
-      assert.equals('.gitignore', filename)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('handles renamed with complex names', function()
-      local buf = create_status_buffer({
-        'Staged (1)',
-        'R  src/old-file.spec.lua -> src/new-file.spec.lua',
-      })
-      local filename, _, _, old_filename = fugitive.get_file_at_line(buf, 2)
-      assert.equals('src/new-file.spec.lua', filename)
-      assert.equals('src/old-file.spec.lua', old_filename)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('handles deeply nested paths', function()
-      local buf = create_status_buffer({
-        'Unstaged (1)',
-        'M  lua/diffs/ui/components/diff-view.lua',
-      })
-      local filename = fugitive.get_file_at_line(buf, 2)
-      assert.equals('lua/diffs/ui/components/diff-view.lua', filename)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('parses untracked file', function()
-      local buf = create_status_buffer({
-        'Untracked (1)',
-        '?  untracked.lua',
-      })
-      local filename, section = fugitive.get_file_at_line(buf, 2)
-      assert.equals('untracked.lua', filename)
-      assert.equals('untracked', section)
+      assert.equals('new name.lua', filename)
+      assert.equals('old name.lua', old_filename)
       vim.api.nvim_buf_delete(buf, { force = true })
     end)
 
@@ -321,30 +254,6 @@ describe('fugitive', function()
       vim.api.nvim_buf_delete(buf, { force = true })
     end)
 
-    it('detects section header for Unstaged', function()
-      local buf = create_status_buffer({
-        'Unstaged (3)',
-        'M  file1.lua',
-      })
-      local filename, section, is_header = fugitive.get_file_at_line(buf, 1)
-      assert.is_nil(filename)
-      assert.equals('unstaged', section)
-      assert.is_true(is_header)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
-    it('detects section header for Untracked', function()
-      local buf = create_status_buffer({
-        'Untracked (1)',
-        '?  newfile.lua',
-      })
-      local filename, section, is_header = fugitive.get_file_at_line(buf, 1)
-      assert.is_nil(filename)
-      assert.equals('untracked', section)
-      assert.is_true(is_header)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
     it('returns is_header=false for file lines', function()
       local buf = create_status_buffer({
         'Staged (1)',
@@ -406,22 +315,6 @@ describe('fugitive', function()
       vim.api.nvim_buf_delete(buf, { force = true })
     end)
 
-    it('returns hunk header and offset for - line', function()
-      local buf = create_status_buffer({
-        'Unstaged (1)',
-        'M  file.lua',
-        '@@ -1,3 +1,3 @@',
-        ' local M = {}',
-        '-local old = false',
-        ' return M',
-      })
-      local pos = fugitive.get_hunk_position(buf, 5)
-      assert.is_not_nil(pos)
-      assert.equals('@@ -1,3 +1,3 @@', pos.hunk_header)
-      assert.equals(2, pos.offset)
-      vim.api.nvim_buf_delete(buf, { force = true })
-    end)
-
     it('returns hunk header and offset for context line', function()
       local buf = create_status_buffer({
         'Unstaged (1)',

spec/gitsigns_spec.lua

@@ -0,0 +1,236 @@
+require('spec.helpers')
+local gs = require('diffs.gitsigns')
+
+local function setup_highlight_groups()
+  local normal = vim.api.nvim_get_hl(0, { name = 'Normal' })
+  local diff_add = vim.api.nvim_get_hl(0, { name = 'DiffAdd' })
+  local diff_delete = vim.api.nvim_get_hl(0, { name = 'DiffDelete' })
+  vim.api.nvim_set_hl(0, 'DiffsClear', { fg = normal.fg or 0xc0c0c0 })
+  vim.api.nvim_set_hl(0, 'DiffsAdd', { bg = diff_add.bg or 0x2e4a3a })
+  vim.api.nvim_set_hl(0, 'DiffsDelete', { bg = diff_delete.bg or 0x4a2e3a })
+  vim.api.nvim_set_hl(0, 'DiffsAddText', { bg = 0x00FF00 })
+  vim.api.nvim_set_hl(0, 'DiffsDeleteText', { bg = 0xFF0000 })
+end
+
+local function create_buffer(lines)
+  local bufnr = vim.api.nvim_create_buf(false, true)
+  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines or {})
+  return bufnr
+end
+
+local function delete_buffer(bufnr)
+  if bufnr and vim.api.nvim_buf_is_valid(bufnr) then
+    vim.api.nvim_buf_delete(bufnr, { force = true })
+  end
+end
+
+describe('gitsigns', function()
+  describe('parse_blame_hunks', function()
+    it('parses a single hunk', function()
+      local bufnr = create_buffer({
+        'commit abc1234',
+        'Author: Test User',
+        '',
+        'Hunk 1 of 1',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        ' local z = 4',
+      })
+      local hunks = gs.parse_blame_hunks(bufnr, 'test.lua', 'lua', 'lua')
+      assert.are.equal(1, #hunks)
+      assert.are.equal('test.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal('lua', hunks[1].lang)
+      assert.are.equal(1, hunks[1].prefix_width)
+      assert.are.equal(0, hunks[1].quote_width)
+      assert.are.equal(4, #hunks[1].lines)
+      assert.are.equal(4, hunks[1].start_line)
+      assert.are.equal(' local x = 1', hunks[1].lines[1])
+      assert.are.equal('-local y = 2', hunks[1].lines[2])
+      assert.are.equal('+local y = 3', hunks[1].lines[3])
+      delete_buffer(bufnr)
+    end)
+
+    it('parses multiple hunks', function()
+      local bufnr = create_buffer({
+        'commit abc1234',
+        '',
+        'Hunk 1 of 2',
+        '-local a = 1',
+        '+local a = 2',
+        'Hunk 2 of 2',
+        ' local b = 3',
+        '+local c = 4',
+      })
+      local hunks = gs.parse_blame_hunks(bufnr, 'test.lua', 'lua', 'lua')
+      assert.are.equal(2, #hunks)
+      assert.are.equal(2, #hunks[1].lines)
+      assert.are.equal(2, #hunks[2].lines)
+      delete_buffer(bufnr)
+    end)
+
+    it('skips guessed-offset lines', function()
+      local bufnr = create_buffer({
+        'commit abc1234',
+        '',
+        'Hunk 1 of 1',
+        '(guessed: hunk offset may be wrong)',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      local hunks = gs.parse_blame_hunks(bufnr, 'test.lua', 'lua', 'lua')
+      assert.are.equal(1, #hunks)
+      assert.are.equal(2, #hunks[1].lines)
+      assert.are.equal(' local x = 1', hunks[1].lines[1])
+      delete_buffer(bufnr)
+    end)
+
+    it('returns empty table when no hunks present', function()
+      local bufnr = create_buffer({
+        'commit abc1234',
+        'Author: Test User',
+        'Date: 2024-01-01',
+      })
+      local hunks = gs.parse_blame_hunks(bufnr, 'test.lua', 'lua', 'lua')
+      assert.are.equal(0, #hunks)
+      delete_buffer(bufnr)
+    end)
+
+    it('handles hunk with no diff lines after header', function()
+      local bufnr = create_buffer({
+        'Hunk 1 of 1',
+        'some non-diff text',
+      })
+      local hunks = gs.parse_blame_hunks(bufnr, 'test.lua', 'lua', 'lua')
+      assert.are.equal(0, #hunks)
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('on_preview', function()
+    before_each(function()
+      setup_highlight_groups()
+    end)
+
+    it('applies extmarks to popup buffer with diff content', function()
+      local bufnr = create_buffer({
+        'commit abc1234',
+        '',
+        'Hunk 1 of 1',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+      })
+
+      local winid = vim.api.nvim_open_win(bufnr, false, {
+        relative = 'editor',
+        width = 40,
+        height = 10,
+        row = 0,
+        col = 0,
+      })
+
+      gs._test.on_preview(winid, bufnr)
+
+      local extmarks = vim.api.nvim_buf_get_extmarks(bufnr, gs._test.ns, 0, -1, { details = true })
+      assert.is_true(#extmarks > 0)
+
+      vim.api.nvim_win_close(winid, true)
+      delete_buffer(bufnr)
+    end)
+
+    it('clears gitsigns_popup namespace on diff region', function()
+      local bufnr = create_buffer({
+        'commit abc1234',
+        '',
+        'Hunk 1 of 1',
+        ' local x = 1',
+        '+local y = 2',
+      })
+
+      vim.api.nvim_buf_set_extmark(bufnr, gs._test.gs_popup_ns, 3, 0, {
+        end_col = 12,
+        hl_group = 'GitSignsAddPreview',
+      })
+      vim.api.nvim_buf_set_extmark(bufnr, gs._test.gs_popup_ns, 4, 0, {
+        end_col = 12,
+        hl_group = 'GitSignsAddPreview',
+      })
+
+      local winid = vim.api.nvim_open_win(bufnr, false, {
+        relative = 'editor',
+        width = 40,
+        height = 10,
+        row = 0,
+        col = 0,
+      })
+
+      gs._test.on_preview(winid, bufnr)
+
+      local gs_extmarks =
+        vim.api.nvim_buf_get_extmarks(bufnr, gs._test.gs_popup_ns, 0, -1, { details = true })
+      assert.are.equal(0, #gs_extmarks)
+
+      vim.api.nvim_win_close(winid, true)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not error on invalid buffer', function()
+      assert.has_no.errors(function()
+        gs._test.on_preview(0, 99999)
+      end)
+    end)
+  end)
+
+  describe('setup', function()
+    it('returns false when gitsigns.popup is not available', function()
+      local saved = package.loaded['gitsigns.popup']
+      package.loaded['gitsigns.popup'] = nil
+      package.preload['gitsigns.popup'] = nil
+
+      local fresh = loadfile('lua/diffs/gitsigns.lua')()
+      local result = fresh.setup()
+      assert.is_false(result)
+
+      package.loaded['gitsigns.popup'] = saved
+    end)
+
+    it('patches gitsigns.popup when available', function()
+      local create_called = false
+      local update_called = false
+      local mock_popup = {
+        create = function()
+          create_called = true
+          local bufnr = create_buffer({ 'test' })
+          local winid = vim.api.nvim_open_win(bufnr, false, {
+            relative = 'editor',
+            width = 10,
+            height = 1,
+            row = 0,
+            col = 0,
+          })
+          return winid, bufnr
+        end,
+        update = function()
+          update_called = true
+        end,
+      }
+
+      local saved = package.loaded['gitsigns.popup']
+      package.loaded['gitsigns.popup'] = mock_popup
+
+      local fresh = loadfile('lua/diffs/gitsigns.lua')()
+      local result = fresh.setup()
+      assert.is_true(result)
+
+      mock_popup.create()
+      assert.is_true(create_called)
+
+      mock_popup.update(0, 0)
+      assert.is_true(update_called)
+
+      package.loaded['gitsigns.popup'] = saved
+    end)
+  end)
+end)

spec/init_spec.lua

@@ -24,7 +24,6 @@ describe('diffs', function()
     it('accepts full config', function()
       vim.g.diffs = {
         debug = true,
-        debounce_ms = 100,
         hide_prefix = false,
         highlights = {
           background = true,
@@ -46,7 +45,7 @@ describe('diffs', function()
 
     it('accepts partial config', function()
       vim.g.diffs = {
-        debounce_ms = 25,
+        hide_prefix = true,
       }
       assert.has_no.errors(function()
         diffs.attach()
@@ -152,6 +151,265 @@ describe('diffs', function()
     end)
   end)
 
+  describe('find_visible_hunks', function()
+    local find_visible_hunks = diffs._test.find_visible_hunks
+
+    local function make_hunk(start_row, end_row, opts)
+      local lines = {}
+      for i = 1, end_row - start_row + 1 do
+        lines[i] = 'line' .. i
+      end
+      local h = { start_line = start_row + 1, lines = lines }
+      if opts and opts.header_start_line then
+        h.header_start_line = opts.header_start_line
+      end
+      return h
+    end
+
+    it('returns (0, 0) for empty hunk list', function()
+      local first, last = find_visible_hunks({}, 0, 50)
+      assert.are.equal(0, first)
+      assert.are.equal(0, last)
+    end)
+
+    it('finds single hunk fully inside viewport', function()
+      local h = make_hunk(5, 10)
+      local first, last = find_visible_hunks({ h }, 0, 50)
+      assert.are.equal(1, first)
+      assert.are.equal(1, last)
+    end)
+
+    it('returns (0, 0) for single hunk fully above viewport', function()
+      local h = make_hunk(5, 10)
+      local first, last = find_visible_hunks({ h }, 20, 50)
+      assert.are.equal(0, first)
+      assert.are.equal(0, last)
+    end)
+
+    it('returns (0, 0) for single hunk fully below viewport', function()
+      local h = make_hunk(50, 60)
+      local first, last = find_visible_hunks({ h }, 0, 20)
+      assert.are.equal(0, first)
+      assert.are.equal(0, last)
+    end)
+
+    it('finds single hunk partially visible at top edge', function()
+      local h = make_hunk(5, 15)
+      local first, last = find_visible_hunks({ h }, 10, 30)
+      assert.are.equal(1, first)
+      assert.are.equal(1, last)
+    end)
+
+    it('finds single hunk partially visible at bottom edge', function()
+      local h = make_hunk(25, 35)
+      local first, last = find_visible_hunks({ h }, 10, 30)
+      assert.are.equal(1, first)
+      assert.are.equal(1, last)
+    end)
+
+    it('finds subset of visible hunks', function()
+      local h1 = make_hunk(5, 10)
+      local h2 = make_hunk(25, 30)
+      local h3 = make_hunk(55, 60)
+      local first, last = find_visible_hunks({ h1, h2, h3 }, 20, 40)
+      assert.are.equal(2, first)
+      assert.are.equal(2, last)
+    end)
+
+    it('finds all hunks when all are visible', function()
+      local h1 = make_hunk(5, 10)
+      local h2 = make_hunk(15, 20)
+      local h3 = make_hunk(25, 30)
+      local first, last = find_visible_hunks({ h1, h2, h3 }, 0, 50)
+      assert.are.equal(1, first)
+      assert.are.equal(3, last)
+    end)
+
+    it('returns (0, 0) when no hunks are visible', function()
+      local h1 = make_hunk(5, 10)
+      local h2 = make_hunk(15, 20)
+      local first, last = find_visible_hunks({ h1, h2 }, 30, 50)
+      assert.are.equal(0, first)
+      assert.are.equal(0, last)
+    end)
+
+    it('uses header_start_line for top boundary', function()
+      local h = make_hunk(5, 10, { header_start_line = 4 })
+      local first, last = find_visible_hunks({ h }, 0, 50)
+      assert.are.equal(1, first)
+      assert.are.equal(1, last)
+    end)
+
+    it('finds both adjacent hunks at viewport edge', function()
+      local h1 = make_hunk(10, 20)
+      local h2 = make_hunk(20, 30)
+      local first, last = find_visible_hunks({ h1, h2 }, 15, 25)
+      assert.are.equal(1, first)
+      assert.are.equal(2, last)
+    end)
+  end)
+
+  describe('hunk_cache', function()
+    local function create_buffer(lines)
+      local bufnr = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines or {})
+      return bufnr
+    end
+
+    local function delete_buffer(bufnr)
+      if vim.api.nvim_buf_is_valid(bufnr) then
+        vim.api.nvim_buf_delete(bufnr, { force = true })
+      end
+    end
+
+    it('creates entry on attach', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.is_table(entry.hunks)
+      assert.is_number(entry.tick)
+      assert.is_true(entry.tick >= 0)
+      delete_buffer(bufnr)
+    end)
+
+    it('is idempotent on repeated attach', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local entry1 = diffs._test.hunk_cache[bufnr]
+      local tick1 = entry1.tick
+      local hunks1 = entry1.hunks
+      diffs._test.ensure_cache(bufnr)
+      local entry2 = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(tick1, entry2.tick)
+      assert.are.equal(hunks1, entry2.hunks)
+      delete_buffer(bufnr)
+    end)
+
+    it('marks stale on invalidate', function()
+      local bufnr = create_buffer({})
+      diffs.attach(bufnr)
+      diffs._test.invalidate_cache(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(-1, entry.tick)
+      assert.is_true(entry.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('evicts on buffer wipeout', function()
+      local bufnr = create_buffer({})
+      diffs.attach(bufnr)
+      assert.is_not_nil(diffs._test.hunk_cache[bufnr])
+      vim.api.nvim_buf_delete(bufnr, { force = true })
+      assert.is_nil(diffs._test.hunk_cache[bufnr])
+    end)
+
+    it('detects content change via tick', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local tick_before = diffs._test.hunk_cache[bufnr].tick
+      vim.api.nvim_buf_set_lines(bufnr, -1, -1, false, { '+local z = 3' })
+      diffs._test.ensure_cache(bufnr)
+      local tick_after = diffs._test.hunk_cache[bufnr].tick
+      assert.is_true(tick_after > tick_before)
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('compute_filetypes', function()
+    local compute = diffs.compute_filetypes
+
+    it('returns core filetypes with empty config', function()
+      local fts = compute({})
+      assert.are.same({ 'git', 'gitcommit' }, fts)
+    end)
+
+    it('includes fugitive when integrations.fugitive = true', function()
+      local fts = compute({ integrations = { fugitive = true } })
+      assert.is_true(vim.tbl_contains(fts, 'fugitive'))
+    end)
+
+    it('includes fugitive when integrations.fugitive is a table', function()
+      local fts = compute({ integrations = { fugitive = { horizontal = 'dd' } } })
+      assert.is_true(vim.tbl_contains(fts, 'fugitive'))
+    end)
+
+    it('excludes fugitive when integrations.fugitive = false', function()
+      local fts = compute({ integrations = { fugitive = false } })
+      assert.is_false(vim.tbl_contains(fts, 'fugitive'))
+    end)
+
+    it('excludes fugitive when integrations.fugitive is nil', function()
+      local fts = compute({ integrations = {} })
+      assert.is_false(vim.tbl_contains(fts, 'fugitive'))
+    end)
+
+    it('includes neogit filetypes when integrations.neogit = true', function()
+      local fts = compute({ integrations = { neogit = true } })
+      assert.is_true(vim.tbl_contains(fts, 'NeogitStatus'))
+      assert.is_true(vim.tbl_contains(fts, 'NeogitCommitView'))
+      assert.is_true(vim.tbl_contains(fts, 'NeogitDiffView'))
+    end)
+
+    it('includes neogit filetypes when integrations.neogit is a table', function()
+      local fts = compute({ integrations = { neogit = {} } })
+      assert.is_true(vim.tbl_contains(fts, 'NeogitStatus'))
+    end)
+
+    it('excludes neogit when integrations.neogit = false', function()
+      local fts = compute({ integrations = { neogit = false } })
+      assert.is_false(vim.tbl_contains(fts, 'NeogitStatus'))
+    end)
+
+    it('excludes neogit when integrations.neogit is nil', function()
+      local fts = compute({ integrations = {} })
+      assert.is_false(vim.tbl_contains(fts, 'NeogitStatus'))
+    end)
+
+    it('includes extra_filetypes', function()
+      local fts = compute({ extra_filetypes = { 'diff' } })
+      assert.is_true(vim.tbl_contains(fts, 'diff'))
+    end)
+
+    it('combines integrations and extra_filetypes', function()
+      local fts = compute({
+        integrations = { fugitive = true, neogit = true },
+        extra_filetypes = { 'diff' },
+      })
+      assert.is_true(vim.tbl_contains(fts, 'git'))
+      assert.is_true(vim.tbl_contains(fts, 'fugitive'))
+      assert.is_true(vim.tbl_contains(fts, 'NeogitStatus'))
+      assert.is_true(vim.tbl_contains(fts, 'diff'))
+    end)
+
+    it('falls back to legacy top-level fugitive key', function()
+      local fts = compute({ fugitive = true })
+      assert.is_true(vim.tbl_contains(fts, 'fugitive'))
+    end)
+
+    it('falls back to legacy top-level neogit key', function()
+      local fts = compute({ neogit = true })
+      assert.is_true(vim.tbl_contains(fts, 'NeogitStatus'))
+    end)
+
+    it('prefers integrations key over legacy top-level key', function()
+      local fts = compute({ integrations = { fugitive = false }, fugitive = true })
+      assert.is_false(vim.tbl_contains(fts, 'fugitive'))
+    end)
+  end)
+
   describe('diff mode', function()
     local function create_diff_window()
       vim.cmd('new')
@@ -269,4 +527,115 @@ describe('diffs', function()
       end)
     end)
   end)
+
+  describe('compute_highlight_groups', function()
+    local saved_get_hl, saved_set_hl, saved_schedule
+    local set_calls, schedule_cbs
+
+    before_each(function()
+      saved_get_hl = vim.api.nvim_get_hl
+      saved_set_hl = vim.api.nvim_set_hl
+      saved_schedule = vim.schedule
+      set_calls = {}
+      schedule_cbs = {}
+      vim.api.nvim_set_hl = function(_, group, opts)
+        set_calls[group] = opts
+      end
+      vim.schedule = function(cb)
+        table.insert(schedule_cbs, cb)
+      end
+      diffs._test.set_hl_retry_pending(false)
+    end)
+
+    after_each(function()
+      vim.api.nvim_get_hl = saved_get_hl
+      vim.api.nvim_set_hl = saved_set_hl
+      vim.schedule = saved_schedule
+      diffs._test.set_hl_retry_pending(false)
+    end)
+
+    it('omits DiffsClear.bg when Normal.bg is nil (transparent)', function()
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          return { fg = 0xc0c0c0 }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      assert.is_nil(set_calls.DiffsClear.bg)
+      assert.is_table(set_calls.DiffsAdd)
+      assert.is_table(set_calls.DiffsDelete)
+    end)
+
+    it('sets DiffsClear.bg to Normal.bg on opaque themes', function()
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          return { fg = 0xebdbb2, bg = 0x282828 }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      assert.are.equal(0x282828, set_calls.DiffsClear.bg)
+    end)
+
+    it('blend_alpha controls DiffsAdd.bg intensity', function()
+      local saved_config_alpha = diffs._test.get_config().highlights.blend_alpha
+      diffs._test.get_config().highlights.blend_alpha = 0.3
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          return { fg = 0xc0c0c0, bg = 0x1e1e2e }
+        end
+        if opts.name == 'DiffAdd' then
+          return { bg = 0x1a3a1a }
+        end
+        if opts.name == 'DiffDelete' then
+          return { bg = 0x3a1a1a }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      local bg_03 = set_calls.DiffsAdd.bg
+
+      diffs._test.get_config().highlights.blend_alpha = 0.9
+      diffs._test.compute_highlight_groups()
+      local bg_09 = set_calls.DiffsAdd.bg
+
+      assert.is_not.equal(bg_03, bg_09)
+
+      diffs._test.get_config().highlights.blend_alpha = saved_config_alpha
+    end)
+
+    it('retries once then stops when Normal.bg stays nil', function()
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          return { fg = 0xc0c0c0 }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      assert.are.equal(1, #schedule_cbs)
+      schedule_cbs[1]()
+      assert.are.equal(1, #schedule_cbs)
+      assert.is_true(diffs._test.get_hl_retry_pending())
+    end)
+
+    it('picks up bg on retry when colorscheme loads late', function()
+      local call_count = 0
+      vim.api.nvim_get_hl = function(ns, opts)
+        if opts.name == 'Normal' then
+          call_count = call_count + 1
+          if call_count <= 1 then
+            return { fg = 0xc0c0c0 }
+          end
+          return { fg = 0xc0c0c0, bg = 0x1e1e2e }
+        end
+        return saved_get_hl(ns, opts)
+      end
+      diffs._test.compute_highlight_groups()
+      assert.are.equal(1, #schedule_cbs)
+      schedule_cbs[1]()
+      assert.are.equal(0x1e1e2e, set_calls.DiffsClear.bg)
+      assert.are.equal(1, #schedule_cbs)
+    end)
+  end)
 end)

spec/integration_spec.lua

@@ -0,0 +1,434 @@
+require('spec.helpers')
+local diffs = require('diffs')
+local highlight = require('diffs.highlight')
+
+local function setup_highlight_groups()
+  local normal = vim.api.nvim_get_hl(0, { name = 'Normal' })
+  local diff_add = vim.api.nvim_get_hl(0, { name = 'DiffAdd' })
+  local diff_delete = vim.api.nvim_get_hl(0, { name = 'DiffDelete' })
+  vim.api.nvim_set_hl(0, 'DiffsClear', { fg = normal.fg or 0xc0c0c0 })
+  vim.api.nvim_set_hl(0, 'DiffsAdd', { bg = diff_add.bg or 0x2e4a3a })
+  vim.api.nvim_set_hl(0, 'DiffsDelete', { bg = diff_delete.bg or 0x4a2e3a })
+  vim.api.nvim_set_hl(0, 'DiffsAddText', { bg = 0x00FF00 })
+  vim.api.nvim_set_hl(0, 'DiffsDeleteText', { bg = 0xFF0000 })
+end
+
+local function create_buffer(lines)
+  local bufnr = vim.api.nvim_create_buf(false, true)
+  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines or {})
+  return bufnr
+end
+
+local function delete_buffer(bufnr)
+  if vim.api.nvim_buf_is_valid(bufnr) then
+    vim.api.nvim_buf_delete(bufnr, { force = true })
+  end
+end
+
+local function get_diffs_ns()
+  return vim.api.nvim_get_namespaces()['diffs']
+end
+
+local function get_extmarks(bufnr, ns)
+  return vim.api.nvim_buf_get_extmarks(bufnr, ns, 0, -1, { details = true })
+end
+
+local function highlight_opts_with_background()
+  return {
+    hide_prefix = false,
+    highlights = {
+      background = true,
+      gutter = false,
+      context = { enabled = false, lines = 0 },
+      treesitter = { enabled = true, max_lines = 500 },
+      vim = { enabled = false, max_lines = 200 },
+      intra = { enabled = false, algorithm = 'default', max_lines = 500 },
+      priorities = { clear = 198, syntax = 199, line_bg = 200, char_bg = 201 },
+    },
+  }
+end
+
+describe('integration', function()
+  before_each(function()
+    setup_highlight_groups()
+  end)
+
+  describe('attach and parse', function()
+    it('attach populates hunk cache for unified diff buffer', function()
+      local bufnr = create_buffer({
+        'diff --git a/foo.lua b/foo.lua',
+        'index abc..def 100644',
+        '--- a/foo.lua',
+        '+++ b/foo.lua',
+        '@@ -1,3 +1,3 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        ' local z = 4',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.are.equal(1, #entry.hunks)
+      assert.are.equal('foo.lua', entry.hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('attach parses multiple hunks across multiple files', function()
+      local bufnr = create_buffer({
+        'M foo.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+        'M bar.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local a = 1',
+        '+local b = 2',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.are.equal(2, #entry.hunks)
+      delete_buffer(bufnr)
+    end)
+
+    it('re-attach on same buffer is idempotent', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local entry_before = diffs._test.hunk_cache[bufnr]
+      local tick_before = entry_before.tick
+      diffs.attach(bufnr)
+      local entry_after = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(tick_before, entry_after.tick)
+      delete_buffer(bufnr)
+    end)
+
+    it('refresh after content change invalidates cache', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local tick_before = diffs._test.hunk_cache[bufnr].tick
+      vim.api.nvim_buf_set_lines(bufnr, -1, -1, false, { '+local z = 3' })
+      diffs.refresh(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(-1, entry.tick)
+      assert.is_true(entry.pending_clear)
+      assert.is_true(tick_before >= 0)
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('ft_retry_pending', function()
+    before_each(function()
+      rawset(vim.fn, 'did_filetype', function()
+        return 1
+      end)
+      require('diffs.parser')._test.ft_lang_cache = {}
+    end)
+
+    after_each(function()
+      rawset(vim.fn, 'did_filetype', nil)
+    end)
+
+    it('sets ft_retry_pending when nil-ft hunks detected under did_filetype', function()
+      local bufnr = create_buffer({
+        'diff --git a/app.conf b/app.conf',
+        '@@ -1,2 +1,2 @@',
+        ' server {',
+        '-    listen 80;',
+        '+    listen 8080;',
+      })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.is_nil(entry.hunks[1].ft)
+      assert.is_true(diffs._test.ft_retry_pending[bufnr] == true)
+      delete_buffer(bufnr)
+    end)
+
+    it('clears ft_retry_pending after scheduled callback fires', function()
+      local bufnr = create_buffer({
+        'diff --git a/app.conf b/app.conf',
+        '@@ -1,2 +1,2 @@',
+        ' server {',
+        '-    listen 80;',
+        '+    listen 8080;',
+      })
+      diffs.attach(bufnr)
+      assert.is_true(diffs._test.ft_retry_pending[bufnr] == true)
+
+      local done = false
+      vim.schedule(function()
+        done = true
+      end)
+      vim.wait(1000, function()
+        return done
+      end)
+
+      assert.is_nil(diffs._test.ft_retry_pending[bufnr])
+      delete_buffer(bufnr)
+    end)
+
+    it('invalidates cache after scheduled callback fires', function()
+      local bufnr = create_buffer({
+        'diff --git a/app.conf b/app.conf',
+        '@@ -1,2 +1,2 @@',
+        ' server {',
+        '-    listen 80;',
+        '+    listen 8080;',
+      })
+      diffs.attach(bufnr)
+      local tick_after_attach = diffs._test.hunk_cache[bufnr].tick
+      assert.is_true(tick_after_attach >= 0)
+
+      local done = false
+      vim.schedule(function()
+        done = true
+      end)
+      vim.wait(1000, function()
+        return done
+      end)
+
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.are.equal(-1, entry.tick)
+      assert.is_true(entry.pending_clear)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not set ft_retry_pending when did_filetype() is zero', function()
+      rawset(vim.fn, 'did_filetype', nil)
+      local bufnr = create_buffer({
+        'diff --git a/test.sh b/test.sh',
+        '@@ -1,2 +1,3 @@',
+        ' #!/usr/bin/env bash',
+        '-old line',
+        '+new line',
+      })
+      diffs.attach(bufnr)
+      assert.is_falsy(diffs._test.ft_retry_pending[bufnr])
+      delete_buffer(bufnr)
+    end)
+
+    it('does not set ft_retry_pending for files with resolvable ft', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      assert.is_falsy(diffs._test.ft_retry_pending[bufnr])
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('extmarks from highlight pipeline', function()
+    it('DiffsAdd background applied to + lines', function()
+      local bufnr = create_buffer({
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      local ns = vim.api.nvim_create_namespace('diffs_integration_test_add')
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2' },
+      }
+      highlight.highlight_hunk(bufnr, ns, hunk, highlight_opts_with_background())
+      local extmarks = get_extmarks(bufnr, ns)
+      local has_diff_add = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].line_hl_group == 'DiffsAdd' then
+          has_diff_add = true
+          break
+        end
+      end
+      assert.is_true(has_diff_add)
+      delete_buffer(bufnr)
+    end)
+
+    it('DiffsDelete background applied to - lines', function()
+      local bufnr = create_buffer({
+        '@@ -1,2 +1,1 @@',
+        ' local x = 1',
+        '-local y = 2',
+      })
+      local ns = vim.api.nvim_create_namespace('diffs_integration_test_del')
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '-local y = 2' },
+      }
+      highlight.highlight_hunk(bufnr, ns, hunk, highlight_opts_with_background())
+      local extmarks = get_extmarks(bufnr, ns)
+      local has_diff_delete = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].line_hl_group == 'DiffsDelete' then
+          has_diff_delete = true
+          break
+        end
+      end
+      assert.is_true(has_diff_delete)
+      delete_buffer(bufnr)
+    end)
+
+    it('mixed hunk produces both DiffsAdd and DiffsDelete backgrounds', function()
+      local bufnr = create_buffer({
+        '@@ -1,2 +1,2 @@',
+        '-local x = 1',
+        '+local x = 2',
+      })
+      local ns = vim.api.nvim_create_namespace('diffs_integration_test_mixed')
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { '-local x = 1', '+local x = 2' },
+      }
+      highlight.highlight_hunk(bufnr, ns, hunk, highlight_opts_with_background())
+      local extmarks = get_extmarks(bufnr, ns)
+      local has_add = false
+      local has_delete = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].line_hl_group == 'DiffsAdd' then
+          has_add = true
+        end
+        if mark[4] and mark[4].line_hl_group == 'DiffsDelete' then
+          has_delete = true
+        end
+      end
+      assert.is_true(has_add)
+      assert.is_true(has_delete)
+      delete_buffer(bufnr)
+    end)
+
+    it('no background extmarks for context lines', function()
+      local bufnr = create_buffer({
+        '@@ -1,3 +1,3 @@',
+        ' local x = 1',
+        '-local y = 2',
+        '+local y = 3',
+        ' local z = 4',
+      })
+      local ns = vim.api.nvim_create_namespace('diffs_integration_test_ctx')
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '-local y = 2', '+local y = 3', ' local z = 4' },
+      }
+      highlight.highlight_hunk(bufnr, ns, hunk, highlight_opts_with_background())
+      local extmarks = get_extmarks(bufnr, ns)
+      local line_bgs = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and (d.line_hl_group == 'DiffsAdd' or d.line_hl_group == 'DiffsDelete') then
+          line_bgs[mark[2]] = d.line_hl_group
+        end
+      end
+      assert.is_nil(line_bgs[1])
+      assert.is_nil(line_bgs[4])
+      assert.are.equal('DiffsDelete', line_bgs[2])
+      assert.are.equal('DiffsAdd', line_bgs[3])
+      delete_buffer(bufnr)
+    end)
+
+    it('treesitter extmarks applied for lua hunks', function()
+      local bufnr = create_buffer({
+        '@@ -1,2 +1,3 @@',
+        ' local x = 1',
+        '+local y = 2',
+        ' return x',
+      })
+      local ns = vim.api.nvim_create_namespace('diffs_integration_test_ts')
+      local hunk = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { ' local x = 1', '+local y = 2', ' return x' },
+      }
+      highlight.highlight_hunk(bufnr, ns, hunk, highlight_opts_with_background())
+      local extmarks = get_extmarks(bufnr, ns)
+      local has_ts = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].hl_group and mark[4].hl_group:match('^@.*%.lua$') then
+          has_ts = true
+          break
+        end
+      end
+      assert.is_true(has_ts)
+      delete_buffer(bufnr)
+    end)
+
+    it('diffs namespace exists after attach', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      diffs.attach(bufnr)
+      local ns = get_diffs_ns()
+      assert.is_not_nil(ns)
+      assert.is_number(ns)
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('multiple hunks highlighting', function()
+    it('both hunks in multi-hunk buffer get background extmarks', function()
+      local bufnr = create_buffer({
+        '@@ -1,2 +1,2 @@',
+        '-local x = 1',
+        '+local x = 10',
+        '@@ -10,2 +10,2 @@',
+        '-local y = 2',
+        '+local y = 20',
+      })
+      local ns = vim.api.nvim_create_namespace('diffs_integration_test_multi')
+      local hunk1 = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 1,
+        lines = { '-local x = 1', '+local x = 10' },
+      }
+      local hunk2 = {
+        filename = 'test.lua',
+        lang = 'lua',
+        start_line = 4,
+        lines = { '-local y = 2', '+local y = 20' },
+      }
+      highlight.highlight_hunk(bufnr, ns, hunk1, highlight_opts_with_background())
+      highlight.highlight_hunk(bufnr, ns, hunk2, highlight_opts_with_background())
+      local extmarks = get_extmarks(bufnr, ns)
+      local add_lines = {}
+      local del_lines = {}
+      for _, mark in ipairs(extmarks) do
+        local d = mark[4]
+        if d and d.line_hl_group == 'DiffsAdd' then
+          add_lines[mark[2]] = true
+        end
+        if d and d.line_hl_group == 'DiffsDelete' then
+          del_lines[mark[2]] = true
+        end
+      end
+      assert.is_true(del_lines[1] ~= nil)
+      assert.is_true(add_lines[2] ~= nil)
+      assert.is_true(del_lines[4] ~= nil)
+      assert.is_true(add_lines[5] ~= nil)
+      delete_buffer(bufnr)
+    end)
+  end)
+end)

spec/merge_spec.lua

@@ -0,0 +1,815 @@
+local helpers = require('spec.helpers')
+local merge = require('diffs.merge')
+
+local function default_config(overrides)
+  local cfg = {
+    enabled = true,
+    disable_diagnostics = false,
+    show_virtual_text = true,
+    show_actions = false,
+    keymaps = {
+      ours = 'doo',
+      theirs = 'dot',
+      both = 'dob',
+      none = 'don',
+      next = ']c',
+      prev = '[c',
+    },
+  }
+  if overrides then
+    cfg = vim.tbl_deep_extend('force', cfg, overrides)
+  end
+  return cfg
+end
+
+local function create_diff_buffer(lines, working_path)
+  local bufnr = helpers.create_buffer(lines)
+  if working_path then
+    vim.api.nvim_buf_set_var(bufnr, 'diffs_working_path', working_path)
+  end
+  return bufnr
+end
+
+local function create_working_buffer(lines, name)
+  local bufnr = vim.api.nvim_create_buf(true, false)
+  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
+  if name then
+    vim.api.nvim_buf_set_name(bufnr, name)
+  end
+  return bufnr
+end
+
+describe('merge', function()
+  describe('parse_hunks', function()
+    it('parses a single hunk', function()
+      local bufnr = helpers.create_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,3 +1,3 @@',
+        ' local M = {}',
+        '-local x = 1',
+        '+local x = 2',
+        ' return M',
+      })
+
+      local hunks = merge.parse_hunks(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.equal(3, hunks[1].start_line)
+      assert.are.equal(7, hunks[1].end_line)
+      assert.are.same({ 'local x = 1' }, hunks[1].del_lines)
+      assert.are.same({ 'local x = 2' }, hunks[1].add_lines)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('parses multiple hunks', function()
+      local bufnr = helpers.create_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,3 +1,3 @@',
+        ' local M = {}',
+        '-local x = 1',
+        '+local x = 2',
+        ' return M',
+        '@@ -10,3 +10,3 @@',
+        ' function M.foo()',
+        '-  return 1',
+        '+  return 2',
+        ' end',
+      })
+
+      local hunks = merge.parse_hunks(bufnr)
+      assert.are.equal(2, #hunks)
+      assert.are.equal(3, hunks[1].start_line)
+      assert.are.equal(8, hunks[2].start_line)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('parses add-only hunk', function()
+      local bufnr = helpers.create_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local new = true',
+        ' return M',
+      })
+
+      local hunks = merge.parse_hunks(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.same({}, hunks[1].del_lines)
+      assert.are.same({ 'local new = true' }, hunks[1].add_lines)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('parses delete-only hunk', function()
+      local bufnr = helpers.create_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,3 +1,2 @@',
+        ' local M = {}',
+        '-local old = false',
+        ' return M',
+      })
+
+      local hunks = merge.parse_hunks(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.same({ 'local old = false' }, hunks[1].del_lines)
+      assert.are.same({}, hunks[1].add_lines)
+
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('returns empty for buffer with no hunks', function()
+      local bufnr = helpers.create_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+      })
+
+      local hunks = merge.parse_hunks(bufnr)
+      assert.are.equal(0, #hunks)
+
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('match_hunk_to_conflict', function()
+    it('matches hunk to conflict region', function()
+      local working_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, '/tmp/diffs_test_match.lua')
+
+      local hunk = {
+        index = 1,
+        start_line = 3,
+        end_line = 7,
+        del_lines = { 'local x = 1' },
+        add_lines = { 'local x = 2' },
+      }
+
+      local region = merge.match_hunk_to_conflict(hunk, working_bufnr)
+      assert.is_not_nil(region)
+      assert.are.equal(0, region.marker_ours)
+
+      helpers.delete_buffer(working_bufnr)
+    end)
+
+    it('returns nil for auto-merged content', function()
+      local working_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, '/tmp/diffs_test_auto.lua')
+
+      local hunk = {
+        index = 1,
+        start_line = 3,
+        end_line = 7,
+        del_lines = { 'local y = 3' },
+        add_lines = { 'local y = 4' },
+      }
+
+      local region = merge.match_hunk_to_conflict(hunk, working_bufnr)
+      assert.is_nil(region)
+
+      helpers.delete_buffer(working_bufnr)
+    end)
+
+    it('matches with empty ours section', function()
+      local working_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, '/tmp/diffs_test_empty_ours.lua')
+
+      local hunk = {
+        index = 1,
+        start_line = 3,
+        end_line = 5,
+        del_lines = {},
+        add_lines = { 'local x = 2' },
+      }
+
+      local region = merge.match_hunk_to_conflict(hunk, working_bufnr)
+      assert.is_not_nil(region)
+
+      helpers.delete_buffer(working_bufnr)
+    end)
+
+    it('matches correct region among multiple conflicts', function()
+      local working_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local a = 1',
+        '=======',
+        'local a = 2',
+        '>>>>>>> feature',
+        'middle',
+        '<<<<<<< HEAD',
+        'local b = 3',
+        '=======',
+        'local b = 4',
+        '>>>>>>> feature',
+      }, '/tmp/diffs_test_multi.lua')
+
+      local hunk = {
+        index = 2,
+        start_line = 8,
+        end_line = 12,
+        del_lines = { 'local b = 3' },
+        add_lines = { 'local b = 4' },
+      }
+
+      local region = merge.match_hunk_to_conflict(hunk, working_bufnr)
+      assert.is_not_nil(region)
+      assert.are.equal(6, region.marker_ours)
+
+      helpers.delete_buffer(working_bufnr)
+    end)
+
+    it('matches with diff3 format', function()
+      local working_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '||||||| base',
+        'local x = 0',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, '/tmp/diffs_test_diff3.lua')
+
+      local hunk = {
+        index = 1,
+        start_line = 3,
+        end_line = 7,
+        del_lines = { 'local x = 1' },
+        add_lines = { 'local x = 2' },
+      }
+
+      local region = merge.match_hunk_to_conflict(hunk, working_bufnr)
+      assert.is_not_nil(region)
+      assert.are.equal(2, region.marker_base)
+
+      helpers.delete_buffer(working_bufnr)
+    end)
+  end)
+
+  describe('resolution', function()
+    local diff_bufnr, working_bufnr
+
+    local function setup_buffers()
+      local working_path = '/tmp/diffs_test_resolve.lua'
+      working_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, working_path)
+
+      diff_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      }, working_path)
+      vim.api.nvim_set_current_buf(diff_bufnr)
+    end
+
+    local function cleanup()
+      helpers.delete_buffer(diff_bufnr)
+      helpers.delete_buffer(working_bufnr)
+    end
+
+    it('resolve_ours keeps ours content in working file', function()
+      setup_buffers()
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      merge.resolve_ours(diff_bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(working_bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('local x = 1', lines[1])
+
+      cleanup()
+    end)
+
+    it('resolve_theirs keeps theirs content in working file', function()
+      setup_buffers()
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      merge.resolve_theirs(diff_bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(working_bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('local x = 2', lines[1])
+
+      cleanup()
+    end)
+
+    it('resolve_both keeps ours then theirs in working file', function()
+      setup_buffers()
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      merge.resolve_both(diff_bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(working_bufnr, 0, -1, false)
+      assert.are.equal(2, #lines)
+      assert.are.equal('local x = 1', lines[1])
+      assert.are.equal('local x = 2', lines[2])
+
+      cleanup()
+    end)
+
+    it('resolve_none removes entire block from working file', function()
+      setup_buffers()
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      merge.resolve_none(diff_bufnr, default_config())
+
+      local lines = vim.api.nvim_buf_get_lines(working_bufnr, 0, -1, false)
+      assert.are.equal(1, #lines)
+      assert.are.equal('', lines[1])
+
+      cleanup()
+    end)
+
+    it('tracks resolved hunks', function()
+      setup_buffers()
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      assert.is_false(merge.is_resolved(diff_bufnr, 1))
+      merge.resolve_ours(diff_bufnr, default_config())
+      assert.is_true(merge.is_resolved(diff_bufnr, 1))
+
+      cleanup()
+    end)
+
+    it('adds virtual text for resolved hunks', function()
+      setup_buffers()
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      merge.resolve_ours(diff_bufnr, default_config())
+
+      local extmarks =
+        vim.api.nvim_buf_get_extmarks(diff_bufnr, merge.get_namespace(), 0, -1, { details = true })
+      local has_resolved_text = false
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          for _, chunk in ipairs(mark[4].virt_text) do
+            if chunk[1]:match('resolved') then
+              has_resolved_text = true
+            end
+          end
+        end
+      end
+      assert.is_true(has_resolved_text)
+
+      cleanup()
+    end)
+
+    it('notifies when hunk is already resolved', function()
+      setup_buffers()
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      merge.resolve_ours(diff_bufnr, default_config())
+
+      local notified = false
+      local orig_notify = vim.notify
+      vim.notify = function(msg)
+        if msg:match('already resolved') then
+          notified = true
+        end
+      end
+
+      merge.resolve_ours(diff_bufnr, default_config())
+      vim.notify = orig_notify
+
+      assert.is_true(notified)
+
+      cleanup()
+    end)
+
+    it('notifies when hunk does not match a conflict', function()
+      local working_path = '/tmp/diffs_test_no_conflict.lua'
+      local w_bufnr = create_working_buffer({
+        'local y = 1',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      local notified = false
+      local orig_notify = vim.notify
+      vim.notify = function(msg)
+        if msg:match('does not correspond') then
+          notified = true
+        end
+      end
+
+      merge.resolve_ours(d_bufnr, default_config())
+      vim.notify = orig_notify
+
+      assert.is_true(notified)
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+  end)
+
+  describe('navigation', function()
+    it('goto_next jumps to next conflict hunk', function()
+      local working_path = '/tmp/diffs_test_nav.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local a = 1',
+        '=======',
+        'local a = 2',
+        '>>>>>>> feature',
+        'middle',
+        '<<<<<<< HEAD',
+        'local b = 3',
+        '=======',
+        'local b = 4',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local a = 1',
+        '+local a = 2',
+        '@@ -5,1 +5,1 @@',
+        '-local b = 3',
+        '+local b = 4',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      merge.goto_next(d_bufnr)
+      assert.are.equal(4, vim.api.nvim_win_get_cursor(0)[1])
+
+      merge.goto_next(d_bufnr)
+      assert.are.equal(7, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+
+    it('goto_next wraps around', function()
+      local working_path = '/tmp/diffs_test_wrap.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 6, 0 })
+
+      merge.goto_next(d_bufnr)
+      assert.are.equal(4, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+
+    it('goto_next notifies on wrap-around', function()
+      local working_path = '/tmp/diffs_test_wrap_notify.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 6, 0 })
+
+      local notified = false
+      local orig_notify = vim.notify
+      vim.notify = function(msg)
+        if msg:match('wrapped to first hunk') then
+          notified = true
+        end
+      end
+
+      merge.goto_next(d_bufnr)
+      vim.notify = orig_notify
+
+      assert.is_true(notified)
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+
+    it('goto_prev jumps to previous conflict hunk', function()
+      local working_path = '/tmp/diffs_test_prev.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local a = 1',
+        '=======',
+        'local a = 2',
+        '>>>>>>> feature',
+        'middle',
+        '<<<<<<< HEAD',
+        'local b = 3',
+        '=======',
+        'local b = 4',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local a = 1',
+        '+local a = 2',
+        '@@ -5,1 +5,1 @@',
+        '-local b = 3',
+        '+local b = 4',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 9, 0 })
+
+      merge.goto_prev(d_bufnr)
+      assert.are.equal(7, vim.api.nvim_win_get_cursor(0)[1])
+
+      merge.goto_prev(d_bufnr)
+      assert.are.equal(4, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+
+    it('goto_prev wraps around', function()
+      local working_path = '/tmp/diffs_test_prev_wrap.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      merge.goto_prev(d_bufnr)
+      assert.are.equal(4, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+
+    it('goto_prev notifies on wrap-around', function()
+      local working_path = '/tmp/diffs_test_prev_wrap_notify.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+
+      local notified = false
+      local orig_notify = vim.notify
+      vim.notify = function(msg)
+        if msg:match('wrapped to last hunk') then
+          notified = true
+        end
+      end
+
+      merge.goto_prev(d_bufnr)
+      vim.notify = orig_notify
+
+      assert.is_true(notified)
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+
+    it('skips resolved hunks', function()
+      local working_path = '/tmp/diffs_test_skip_resolved.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local a = 1',
+        '=======',
+        'local a = 2',
+        '>>>>>>> feature',
+        'middle',
+        '<<<<<<< HEAD',
+        'local b = 3',
+        '=======',
+        'local b = 4',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local a = 1',
+        '+local a = 2',
+        '@@ -5,1 +5,1 @@',
+        '-local b = 3',
+        '+local b = 4',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      merge.resolve_ours(d_bufnr, default_config())
+
+      vim.api.nvim_win_set_cursor(0, { 1, 0 })
+      merge.goto_next(d_bufnr)
+      assert.are.equal(7, vim.api.nvim_win_get_cursor(0)[1])
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+  end)
+
+  describe('hunk hints', function()
+    it('adds keymap hints on hunk header lines', function()
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      })
+
+      merge.setup_keymaps(d_bufnr, default_config())
+
+      local extmarks =
+        vim.api.nvim_buf_get_extmarks(d_bufnr, merge.get_namespace(), 0, -1, { details = true })
+      local hint_marks = {}
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          local text = ''
+          for _, chunk in ipairs(mark[4].virt_text) do
+            text = text .. chunk[1]
+          end
+          table.insert(hint_marks, { line = mark[2], text = text })
+        end
+      end
+      assert.are.equal(1, #hint_marks)
+      assert.are.equal(3, hint_marks[1].line)
+      assert.is_truthy(hint_marks[1].text:find('doo'))
+      assert.is_truthy(hint_marks[1].text:find('dot'))
+
+      helpers.delete_buffer(d_bufnr)
+    end)
+  end)
+
+  describe('setup_keymaps', function()
+    it('clears resolved state on re-init', function()
+      local working_path = '/tmp/diffs_test_reinit.lua'
+      local w_bufnr = create_working_buffer({
+        '<<<<<<< HEAD',
+        'local x = 1',
+        '=======',
+        'local x = 2',
+        '>>>>>>> feature',
+      }, working_path)
+
+      local d_bufnr = create_diff_buffer({
+        'diff --git a/file.lua b/file.lua',
+        '--- a/file.lua',
+        '+++ b/file.lua',
+        '@@ -1,1 +1,1 @@',
+        '-local x = 1',
+        '+local x = 2',
+      }, working_path)
+      vim.api.nvim_set_current_buf(d_bufnr)
+      vim.api.nvim_win_set_cursor(0, { 5, 0 })
+
+      local cfg = default_config()
+      merge.resolve_ours(d_bufnr, cfg)
+      assert.is_true(merge.is_resolved(d_bufnr, 1))
+
+      local extmarks =
+        vim.api.nvim_buf_get_extmarks(d_bufnr, merge.get_namespace(), 0, -1, { details = true })
+      assert.is_true(#extmarks > 0)
+
+      merge.setup_keymaps(d_bufnr, cfg)
+
+      assert.is_false(merge.is_resolved(d_bufnr, 1))
+      extmarks =
+        vim.api.nvim_buf_get_extmarks(d_bufnr, merge.get_namespace(), 0, -1, { details = true })
+      local resolved_count = 0
+      for _, mark in ipairs(extmarks) do
+        if mark[4] and mark[4].virt_text then
+          for _, chunk in ipairs(mark[4].virt_text) do
+            if chunk[1]:match('resolved') then
+              resolved_count = resolved_count + 1
+            end
+          end
+        end
+      end
+      assert.are.equal(0, resolved_count)
+
+      helpers.delete_buffer(d_bufnr)
+      helpers.delete_buffer(w_bufnr)
+    end)
+  end)
+
+  describe('fugitive integration', function()
+    it('parse_file_line returns status for unmerged files', function()
+      local fugitive = require('diffs.fugitive')
+      local buf = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_lines(buf, 0, -1, false, {
+        'Unstaged (1)',
+        'U  conflict.lua',
+      })
+      local filename, section, is_header, old_filename, status = fugitive.get_file_at_line(buf, 2)
+      assert.are.equal('conflict.lua', filename)
+      assert.are.equal('unstaged', section)
+      assert.is_false(is_header)
+      assert.is_nil(old_filename)
+      assert.are.equal('U', status)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('walkback from hunk line propagates status', function()
+      local fugitive = require('diffs.fugitive')
+      local buf = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_lines(buf, 0, -1, false, {
+        'Unstaged (1)',
+        'U  conflict.lua',
+        '@@ -1,3 +1,4 @@',
+        ' local M = {}',
+        '+local new = true',
+      })
+      local _, _, _, _, status = fugitive.get_file_at_line(buf, 5)
+      assert.are.equal('U', status)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+  end)
+end)

spec/neogit_integration_spec.lua

@@ -0,0 +1,126 @@
+require('spec.helpers')
+
+vim.g.diffs = { integrations = { neogit = true } }
+
+local diffs = require('diffs')
+local parser = require('diffs.parser')
+
+local function create_buffer(lines)
+  local bufnr = vim.api.nvim_create_buf(false, true)
+  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines or {})
+  return bufnr
+end
+
+local function delete_buffer(bufnr)
+  if vim.api.nvim_buf_is_valid(bufnr) then
+    vim.api.nvim_buf_delete(bufnr, { force = true })
+  end
+end
+
+describe('neogit_integration', function()
+  describe('neogit_disable_hunk_highlight', function()
+    it('sets neogit_disable_hunk_highlight on NeogitStatus buffer after attach', function()
+      local bufnr = create_buffer({
+        'modified   test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      vim.api.nvim_set_option_value('filetype', 'NeogitStatus', { buf = bufnr })
+      diffs.attach(bufnr)
+
+      assert.is_true(vim.b[bufnr].neogit_disable_hunk_highlight)
+
+      delete_buffer(bufnr)
+    end)
+
+    it('does not set neogit_disable_hunk_highlight on non-Neogit buffer', function()
+      local bufnr = create_buffer({})
+      vim.api.nvim_set_option_value('filetype', 'git', { buf = bufnr })
+      diffs.attach(bufnr)
+
+      assert.is_not_true(vim.b[bufnr].neogit_disable_hunk_highlight)
+
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('NeogitStatus buffer attach', function()
+    it('populates hunk_cache for NeogitStatus buffer with diff content', function()
+      local bufnr = create_buffer({
+        'modified   hello.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local x = 1',
+        ' return M',
+      })
+      vim.api.nvim_set_option_value('filetype', 'NeogitStatus', { buf = bufnr })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.is_table(entry.hunks)
+      assert.are.equal(1, #entry.hunks)
+      assert.are.equal('hello.lua', entry.hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('populates hunk_cache for NeogitDiffView buffer', function()
+      local bufnr = create_buffer({
+        'new file   newmod.lua',
+        '@@ -0,0 +1,2 @@',
+        '+local M = {}',
+        '+return M',
+      })
+      vim.api.nvim_set_option_value('filetype', 'NeogitDiffView', { buf = bufnr })
+      diffs.attach(bufnr)
+      local entry = diffs._test.hunk_cache[bufnr]
+      assert.is_not_nil(entry)
+      assert.is_table(entry.hunks)
+      assert.are.equal(1, #entry.hunks)
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('parser neogit patterns', function()
+    it('detects renamed prefix via parser', function()
+      local bufnr = create_buffer({
+        'renamed   old.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local x = 1',
+        ' return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.equal('old.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects copied prefix via parser', function()
+      local bufnr = create_buffer({
+        'copied   orig.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local x = 1',
+        ' return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.equal('orig.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects deleted prefix via parser', function()
+      local bufnr = create_buffer({
+        'deleted   gone.lua',
+        '@@ -1,2 +0,0 @@',
+        '-local M = {}',
+        '-return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.equal('gone.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+  end)
+end)

spec/parser_spec.lua

@@ -163,10 +163,10 @@ describe('parser', function()
       end
     end)
 
-    it('stops hunk at blank line', function()
+    it('stops hunk at blank line when remaining counts exhausted', function()
       local bufnr = create_buffer({
         'M test.lua',
-        '@@ -1,2 +1,3 @@',
+        '@@ -1,1 +1,2 @@',
         ' local x = 1',
         '+local y = 2',
         '',
@@ -391,35 +391,27 @@ describe('parser', function()
       vim.fn.delete(repo_root, 'rf')
     end)
 
-    it('detects python from shebang without open buffer', function()
-      local repo_root = '/tmp/diffs-test-shebang-py'
-      vim.fn.mkdir(repo_root, 'p')
+    it('detects filetype for .sh files when did_filetype() is non-zero', function()
+      rawset(vim.fn, 'did_filetype', function()
+        return 1
+      end)
 
-      local file_path = repo_root .. '/deploy'
-      local f = io.open(file_path, 'w')
-      f:write('#!/usr/bin/env python3\n')
-      f:write('import sys\n')
-      f:write('print("hi")\n')
-      f:close()
-
-      local diff_buf = create_buffer({
-        'M deploy',
-        '@@ -1,2 +1,3 @@',
-        ' #!/usr/bin/env python3',
-        '+import sys',
-        ' print("hi")',
+      parser._test.ft_lang_cache = {}
+      local bufnr = create_buffer({
+        'diff --git a/test.sh b/test.sh',
+        '@@ -1,3 +1,4 @@',
+        ' #!/usr/bin/env bash',
+        ' set -euo pipefail',
+        '-echo "running tests..."',
+        '+echo "running tests with coverage..."',
       })
-      vim.api.nvim_buf_set_var(diff_buf, 'diffs_repo_root', repo_root)
-
-      local hunks = parser.parse_buffer(diff_buf)
+      local hunks = parser.parse_buffer(bufnr)
 
       assert.are.equal(1, #hunks)
-      assert.are.equal('deploy', hunks[1].filename)
-      assert.are.equal('python', hunks[1].ft)
-
-      delete_buffer(diff_buf)
-      os.remove(file_path)
-      vim.fn.delete(repo_root, 'rf')
+      assert.are.equal('test.sh', hunks[1].filename)
+      assert.are.equal('sh', hunks[1].ft)
+      delete_buffer(bufnr)
+      rawset(vim.fn, 'did_filetype', nil)
     end)
 
     it('extracts file line numbers from @@ header', function()
@@ -440,22 +432,6 @@ describe('parser', function()
       delete_buffer(bufnr)
     end)
 
-    it('extracts large line numbers from @@ header', function()
-      local bufnr = create_buffer({
-        'M lua/test.lua',
-        '@@ -100,20 +200,30 @@',
-        ' local M = {}',
-      })
-      local hunks = parser.parse_buffer(bufnr)
-
-      assert.are.equal(1, #hunks)
-      assert.are.equal(100, hunks[1].file_old_start)
-      assert.are.equal(20, hunks[1].file_old_count)
-      assert.are.equal(200, hunks[1].file_new_start)
-      assert.are.equal(30, hunks[1].file_new_count)
-      delete_buffer(bufnr)
-    end)
-
     it('defaults count to 1 when omitted in @@ header', function()
       local bufnr = create_buffer({
         'M lua/test.lua',
@@ -472,6 +448,154 @@ describe('parser', function()
       delete_buffer(bufnr)
     end)
 
+    it('recognizes U prefix for unmerged files', function()
+      local bufnr = create_buffer({
+        'U merge_me.lua',
+        '@@@ -1,3 -1,5 +1,9 @@@',
+        '  local M = {}',
+        '++<<<<<<< HEAD',
+        ' +  return 1',
+        '++=======',
+        '+   return 2',
+        '++>>>>>>> feature',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('merge_me.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      delete_buffer(bufnr)
+    end)
+
+    it('sets prefix_width 2 from @@@ combined diff header', function()
+      local bufnr = create_buffer({
+        'U test.lua',
+        '@@@ -1,3 -1,5 +1,9 @@@',
+        '  local M = {}',
+        '++<<<<<<< HEAD',
+        ' +  return 1',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(2, hunks[1].prefix_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('sets prefix_width 1 for standard @@ unified diff', function()
+      local bufnr = create_buffer({
+        'M test.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(1, hunks[1].prefix_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('collects all combined diff line types as hunk content', function()
+      local bufnr = create_buffer({
+        'U test.lua',
+        '@@@ -1,3 -1,3 +1,5 @@@',
+        '  local M = {}',
+        '++<<<<<<< HEAD',
+        ' +  return 1',
+        '+ local x = 2',
+        '  end',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(5, #hunks[1].lines)
+      assert.are.equal('  local M = {}', hunks[1].lines[1])
+      assert.are.equal('++<<<<<<< HEAD', hunks[1].lines[2])
+      assert.are.equal(' +  return 1', hunks[1].lines[3])
+      assert.are.equal('+ local x = 2', hunks[1].lines[4])
+      assert.are.equal('  end', hunks[1].lines[5])
+      delete_buffer(bufnr)
+    end)
+
+    it('extracts new range from combined diff header', function()
+      local bufnr = create_buffer({
+        'U test.lua',
+        '@@@ -1,3 -1,5 +1,9 @@@',
+        '  local M = {}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal(1, hunks[1].file_new_start)
+      assert.are.equal(9, hunks[1].file_new_count)
+      assert.are.equal(1, hunks[1].file_old_start)
+      assert.are.equal(3, hunks[1].file_old_count)
+      delete_buffer(bufnr)
+    end)
+
+    it('extracts header context from combined diff header', function()
+      local bufnr = create_buffer({
+        'U test.lua',
+        '@@@ -1,3 -1,5 +1,9 @@@ function M.greet()',
+        '  local M = {}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('function M.greet()', hunks[1].header_context)
+      delete_buffer(bufnr)
+    end)
+
+    it('resets prefix_width when switching from combined to unified diff', function()
+      local bufnr = create_buffer({
+        'U merge.lua',
+        '@@@ -1,1 -1,1 +1,3 @@@',
+        '  local M = {}',
+        '++<<<<<<< HEAD',
+        'M other.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(2, #hunks)
+      assert.are.equal(2, hunks[1].prefix_width)
+      assert.are.equal(1, hunks[2].prefix_width)
+      delete_buffer(bufnr)
+    end)
+
+    it('parses diff from gitcommit verbose buffer', function()
+      local bufnr = create_buffer({
+        '',
+        '# Please enter the commit message for your changes.',
+        '#',
+        '# On branch main',
+        '# Changes to be committed:',
+        '#\tmodified:   test.lua',
+        '#',
+        '# ------------------------ >8 ------------------------',
+        '# Do not modify or remove the line above.',
+        'diff --git a/test.lua b/test.lua',
+        'index abc1234..def5678 100644',
+        '--- a/test.lua',
+        '+++ b/test.lua',
+        '@@ -1,3 +1,3 @@',
+        ' local function hello()',
+        '-  print("hello world")',
+        '+  print("hello universe")',
+        '   return true',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('test.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal(4, #hunks[1].lines)
+      delete_buffer(bufnr)
+    end)
+
     it('stores repo_root on hunk when available', function()
       local bufnr = create_buffer({
         'M lua/test.lua',
@@ -488,16 +612,388 @@ describe('parser', function()
       delete_buffer(bufnr)
     end)
 
-    it('repo_root is nil when not available', function()
+    it('detects neogit modified prefix', function()
       local bufnr = create_buffer({
-        'M lua/test.lua',
-        '@@ -1,3 +1,4 @@',
+        'modified   hello.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local x = 1',
+        ' return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('hello.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal(3, #hunks[1].lines)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects neogit new file prefix', function()
+      local bufnr = create_buffer({
+        'new file   hello.lua',
+        '@@ -0,0 +1,2 @@',
+        '+local M = {}',
+        '+return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('hello.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal(2, #hunks[1].lines)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects neogit deleted prefix', function()
+      local bufnr = create_buffer({
+        'deleted   hello.lua',
+        '@@ -1,2 +0,0 @@',
+        '-local M = {}',
+        '-return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('hello.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal(2, #hunks[1].lines)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects neogit renamed prefix', function()
+      local bufnr = create_buffer({
+        'renamed   old.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local x = 1',
+        ' return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('old.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects neogit copied prefix', function()
+      local bufnr = create_buffer({
+        'copied   orig.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local x = 1',
+        ' return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('orig.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "new file mode" as a filename', function()
+      local bufnr = create_buffer({
+        'diff --git a/src/new.lua b/src/new.lua',
+        'new file mode 100644',
+        'index 0000000..abc1234',
+        '--- /dev/null',
+        '+++ b/src/new.lua',
+        '@@ -0,0 +1,2 @@',
+        '+local M = {}',
+        '+return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('src/new.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "new file mode 100755" as a filename', function()
+      local bufnr = create_buffer({
+        'diff --git a/bin/run b/bin/run',
+        'new file mode 100755',
+        'index 0000000..abc1234',
+        '--- /dev/null',
+        '+++ b/bin/run',
+        '@@ -0,0 +1,2 @@',
+        '+#!/bin/bash',
+        '+echo hello',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('bin/run', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "deleted file mode" as a filename', function()
+      local bufnr = create_buffer({
+        'diff --git a/src/old.lua b/src/old.lua',
+        'deleted file mode 100644',
+        'index abc1234..0000000',
+        '--- a/src/old.lua',
+        '+++ /dev/null',
+        '@@ -1,2 +0,0 @@',
+        '-local M = {}',
+        '-return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('src/old.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "deleted file mode 100755" as a filename', function()
+      local bufnr = create_buffer({
+        'diff --git a/bin/old b/bin/old',
+        'deleted file mode 100755',
+        'index abc1234..0000000',
+        '--- a/bin/old',
+        '+++ /dev/null',
+        '@@ -1,1 +0,0 @@',
+        '-#!/bin/bash',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('bin/old', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "old mode" or "new mode" as filenames', function()
+      local bufnr = create_buffer({
+        'diff --git a/script.sh b/script.sh',
+        'old mode 100644',
+        'new mode 100755',
+        '@@ -1,1 +1,2 @@',
+        ' echo hello',
+        '+echo world',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('script.sh', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "rename from/to" as filenames', function()
+      local bufnr = create_buffer({
+        'diff --git a/old.lua b/new.lua',
+        'similarity index 95%',
+        'rename from old.lua',
+        'rename to new.lua',
+        '@@ -1,2 +1,2 @@',
+        ' local M = {}',
+        '-local x = 1',
+        '+local x = 2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('new.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "copy from/to" as filenames', function()
+      local bufnr = create_buffer({
+        'diff --git a/orig.lua b/copy.lua',
+        'similarity index 100%',
+        'copy from orig.lua',
+        'copy to copy.lua',
+        '@@ -1,1 +1,1 @@',
         ' local M = {}',
       })
       local hunks = parser.parse_buffer(bufnr)
 
       assert.are.equal(1, #hunks)
-      assert.is_nil(hunks[1].repo_root)
+      assert.are.equal('copy.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "similarity index" or "dissimilarity index" as filenames', function()
+      local bufnr = create_buffer({
+        'diff --git a/foo.lua b/bar.lua',
+        'similarity index 85%',
+        'rename from foo.lua',
+        'rename to bar.lua',
+        '@@ -1,2 +1,2 @@',
+        ' local M = {}',
+        '-return 1',
+        '+return 2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('bar.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not treat "index" line as a filename', function()
+      local bufnr = create_buffer({
+        'diff --git a/test.lua b/test.lua',
+        'index abc1234..def5678 100644',
+        '--- a/test.lua',
+        '+++ b/test.lua',
+        '@@ -1,1 +1,2 @@',
+        ' local x = 1',
+        '+local y = 2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('test.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('neogit new file with diff containing new file mode metadata', function()
+      local bufnr = create_buffer({
+        'new file   src/foo.lua',
+        'diff --git a/src/foo.lua b/src/foo.lua',
+        'new file mode 100644',
+        'index 0000000..abc1234',
+        '--- /dev/null',
+        '+++ b/src/foo.lua',
+        '@@ -0,0 +1,3 @@',
+        '+local M = {}',
+        '+M.x = 1',
+        '+return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('src/foo.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal(3, #hunks[1].lines)
+      delete_buffer(bufnr)
+    end)
+
+    it('neogit deleted with diff containing deleted file mode metadata', function()
+      local bufnr = create_buffer({
+        'deleted   src/old.lua',
+        'diff --git a/src/old.lua b/src/old.lua',
+        'deleted file mode 100644',
+        'index abc1234..0000000',
+        '--- a/src/old.lua',
+        '+++ /dev/null',
+        '@@ -1,2 +0,0 @@',
+        '-local M = {}',
+        '-return M',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('src/old.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal(2, #hunks[1].lines)
+      delete_buffer(bufnr)
+    end)
+
+    it('multiple new files with mode metadata do not corrupt filenames', function()
+      local bufnr = create_buffer({
+        'diff --git a/a.lua b/a.lua',
+        'new file mode 100644',
+        'index 0000000..abc1234',
+        '--- /dev/null',
+        '+++ b/a.lua',
+        '@@ -0,0 +1,1 @@',
+        '+local a = 1',
+        'diff --git a/b.lua b/b.lua',
+        'new file mode 100644',
+        'index 0000000..def5678',
+        '--- /dev/null',
+        '+++ b/b.lua',
+        '@@ -0,0 +1,1 @@',
+        '+local b = 2',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(2, #hunks)
+      assert.are.equal('a.lua', hunks[1].filename)
+      assert.are.equal('b.lua', hunks[2].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('fugitive status with new and deleted files containing mode metadata', function()
+      local bufnr = create_buffer({
+        'Head: main',
+        '',
+        'Staged (2)',
+        'A src/new.lua',
+        'diff --git a/src/new.lua b/src/new.lua',
+        'new file mode 100644',
+        'index 0000000..abc1234',
+        '--- /dev/null',
+        '+++ b/src/new.lua',
+        '@@ -0,0 +1,2 @@',
+        '+local M = {}',
+        '+return M',
+        'D src/old.lua',
+        'diff --git a/src/old.lua b/src/old.lua',
+        'deleted file mode 100644',
+        'index abc1234..0000000',
+        '--- a/src/old.lua',
+        '+++ /dev/null',
+        '@@ -1,1 +0,0 @@',
+        '-local x = 1',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(2, #hunks)
+      assert.are.equal('src/new.lua', hunks[1].filename)
+      assert.are.equal('lua', hunks[1].ft)
+      assert.are.equal('src/old.lua', hunks[2].filename)
+      assert.are.equal('lua', hunks[2].ft)
+      delete_buffer(bufnr)
+    end)
+
+    it('neogit new file with deep nested path', function()
+      local bufnr = create_buffer({
+        'new file   src/deep/nested/path/module.lua',
+        '@@ -0,0 +1,1 @@',
+        '+return {}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('src/deep/nested/path/module.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects bare filename for untracked files', function()
+      local bufnr = create_buffer({
+        'newfile.rs',
+        '@@ -0,0 +1,3 @@',
+        '+fn main() {',
+        '+    println!("hello");',
+        '+}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('newfile.rs', hunks[1].filename)
+      assert.are.equal(3, #hunks[1].lines)
+      delete_buffer(bufnr)
+    end)
+
+    it('does not match section headers as bare filenames', function()
+      local bufnr = create_buffer({
+        'Untracked files (1)',
+        'newfile.rs',
+        '@@ -0,0 +1,3 @@',
+        '+fn main() {',
+        '+    println!("hello");',
+        '+}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+
+      assert.are.equal(1, #hunks)
+      assert.are.equal('newfile.rs', hunks[1].filename)
       delete_buffer(bufnr)
     end)
   end)

vim.toml

@@ -1,33 +0,0 @@
-[selene]
-base = "lua51"
-name = "vim"
-
-[vim]
-any = true
-
-[jit]
-any = true
-
-[bit]
-any = true
-
-[assert]
-any = true
-
-[describe]
-any = true
-
-[it]
-any = true
-
-[before_each]
-any = true
-
-[after_each]
-any = true
-
-[spy]
-any = true
-
-[stub]
-any = true

vim.yaml

@@ -0,0 +1,26 @@
+---
+base: lua51
+name: vim
+lua_versions:
+  - luajit
+globals:
+  vim:
+    any: true
+  jit:
+    any: true
+  assert:
+    any: true
+  describe:
+    any: true
+  it:
+    any: true
+  before_each:
+    any: true
+  after_each:
+    any: true
+  spy:
+    any: true
+  stub:
+    any: true
+  bit:
+    any: true