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diffs.nvim/README.md
Barrett Ruth 7106bcc291
refactor(highlight): unified per-line extmark builder (#144) 
## Problem

`highlight_hunk` applied DiffsClear extmarks across 5 scattered sites
with
ad-hoc column arithmetic. This fragmentation produced the 1-column
DiffsClear
gap on email-quoted body context lines (#142 issue 1). A redundant
`highlight_hunk_vim_syntax` function duplicated the inline vim syntax
path,
and the deferred pass in init.lua double-called it, creating duplicate
scratch
buffers and extmarks.

## Solution

Reorganize `highlight_hunk` into two clean phases:

- **Phase 1** — multi-line syntax computation (treesitter, vim syntax,
diff
grammar, header context text). Sets syntax extmarks only, no DiffsClear.
- **Phase 2** — per-line chrome (DiffsClear, backgrounds, gutter,
overlays,
  intra-line). All non-syntax extmarks consolidated in one pass.

Hoist `new_code` to function scope (needed by `highlight_text` outside
the
`use_ts` block). Hoist `at_raw_line` so Phase 1d and Phase 2b share one
`nvim_buf_get_lines` call.

Delete `highlight_hunk_vim_syntax` (redundant with inline path). Remove
the
double-call from the deferred pass in init.lua.

Extend body prefix DiffsClear `end_col` from `qw` to `pw + qw`, fixing
the
1-column gap where native treesitter background bled through on context
lines
in email-quoted diffs (#142 issue 1).

### Email-quoted diff support

The parser now strips `> ` (and `>> `, etc.) email quote prefixes before
pattern matching, enabling syntax highlighting for diffs embedded in
email
replies and `git-send-email` / sourcehut-style patch review threads.
Each hunk stores `quote_width` so the highlight pipeline can apply
`DiffsClear` at the correct column offsets to suppress native treesitter
on quoted regions.

Closes #141

### #142 status after this PR

| Sub-issue | Status |
|-----------|--------|
| 1. Col gap on context lines | Fixed |
| 2. Bare `>` context lines | Improved, edge case remains |
| 3. Diff prefix marker fg | Not addressed (follow-up) |
2026-03-05 09:01:22 -05:00

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diffs.nvim

Syntax highlighting for diffs in Neovim

Enhance vim-fugitive, Neogit, and Neovim's built-in diff mode with language-aware syntax highlighting.

Features

  • Treesitter syntax highlighting in vim-fugitive, Neogit, and diff filetype
  • Character-level intra-line diff highlighting (with optional vscode-diff FFI backend for word-level accuracy)
  • :Gdiff unified diff against any revision
  • Background-only diff colors for &diff buffers
  • Inline merge conflict detection, highlighting, and resolution
  • Email-quoted diff highlighting (> diff ... prefixes, arbitrary nesting depth)
  • Vim syntax fallback, configurable blend/priorities

Requirements

  • Neovim 0.9.0+

Installation

Install with your package manager of choice or via luarocks:

luarocks install diffs.nvim

Documentation

:help diffs.nvim

FAQ

Q: How do I install with lazy.nvim?

{
  '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?

Yes. Enable it in your config:

vim.g.diffs = {
  fugitive = true,
  neogit = true,
}

See the documentation for more information.

Known Limitations

  • Incomplete syntax context: Treesitter parses each diff hunk in isolation. 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 triggered by vim-fugitive, at which point the buffer is preliminarily 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:

    • diffview.nvim - provides its own diff highlighting and conflict resolution UI
    • mini.diff - visualizes buffer differences with its own highlighting system
    • gitsigns.nvim - generally compatible, but both plugins modifying line highlights may produce unexpected results
    • git-conflict.nvim - diffs.nvim now includes built-in conflict resolution; disable one or the other to avoid overlap

Acknowledgements