feat(neojj): add neojj (jujutsu) integration

Problem: diffs.nvim has no support for neojj, the neogit-like TUI for
jujutsu VCS. Users switching to jj get no syntax highlighting in neojj
status/diff buffers.

Solution: Mirror the existing neogit integration pattern for neojj.
Register `NeojjStatus`, `NeojjCommitView`, `NeojjDiffView` filetypes,
set `vim.b.neojj_disable_hunk_highlight` on attach, listen for
`User NeojjDiffLoaded` events, and detect jj repo root via
`neojj.lib.jj.repo.worktree_root`. Add parser patterns for neojj's
`added`, `updated`, `changed`, and `unmerged` filename labels.

README.md

@@ -9,7 +9,10 @@ highlighting driven by treesitter.
 
 ## Features
 
-- Treesitter syntax highlighting in vim-fugitive, Neogit, and `diff` filetype
+- Treesitter syntax highlighting in
+  [vim-fugitive](https://github.com/tpope/vim-fugitive),
+  [Neogit](https://github.com/NeogitOrg/neogit), builtin `diff` filetype, and
+  more!
 - Character-level intra-line diff highlighting (with optional
   [vscode-diff](https://github.com/esmuellert/codediff.nvim) FFI backend for
   word-level accuracy)
@@ -58,15 +61,18 @@ luarocks install diffs.nvim
 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?**
+**Q: Does diffs.nvim support vim-fugitive/Neogit/neojj/gitsigns?**
 
 Yes. Enable integrations in your config:
 
 ```lua
 vim.g.diffs = {
-  fugitive = true,
+  integrations = {
-  neogit = true,
+    fugitive = true,
-  gitsigns = true,
+    neogit = true,
+    neojj = true,
+    gitsigns = true,
+  }
 }
 ```
 

doc/diffs.nvim.txt

@@ -40,6 +40,7 @@ CONTENTS                                                      *diffs-contents*
   7. Integrations ..................................... |diffs-integrations|
        Fugitive .......................................... |diffs-fugitive|
        Neogit .............................................. |diffs-neogit|
+       Neojj ............................................... |diffs-neojj|
        Gitsigns .......................................... |diffs-gitsigns|
        Telescope ........................................ |diffs-telescope|
   8. Conflict Resolution .................................... |diffs-conflict|
@@ -84,6 +85,7 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
       integrations = {
         fugitive = false,
         neogit = false,
+        neojj = false,
         gitsigns = false,
         committia = false,
         telescope = false,
@@ -180,6 +182,14 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                                  integrations = { neogit = true }
 <
 
+            {neojj}          (boolean|table, default: false)
+                             Enable neojj integration. When active,
+                             `NeojjStatus`, `NeojjCommitView`, and
+                             `NeojjDiffView` filetypes are registered.
+                             See |diffs-neojj|. >lua
+                                 integrations = { neojj = true }
+<
+
             {gitsigns}       (boolean|table, default: false)
                              Enable gitsigns.nvim blame popup highlighting.
                              See |diffs-gitsigns|. >lua
@@ -536,6 +546,7 @@ each integration's filetypes and attaches automatically.
       integrations = {
         fugitive = true,
         neogit = true,
+        neojj = true,
         gitsigns = true,
       },
     }
@@ -624,6 +635,17 @@ 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.
 
+------------------------------------------------------------------------------
+NEOJJ                                                            *diffs-neojj*
+
+Enable neojj (https://github.com/NicholasZolton/neojj) support: >lua
+    vim.g.diffs = { integrations = { neojj = true } }
+<
+
+Expanding a diff in a neojj 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*
 

lua/diffs/init.lua

@@ -39,6 +39,8 @@
 
 ---@class diffs.NeogitConfig
 
+---@class diffs.NeojjConfig
+
 ---@class diffs.GitsignsConfig
 
 ---@class diffs.CommittiaConfig
@@ -65,6 +67,7 @@
 ---@class diffs.IntegrationsConfig
 ---@field fugitive diffs.FugitiveConfig|false
 ---@field neogit diffs.NeogitConfig|false
+---@field neojj diffs.NeojjConfig|false
 ---@field gitsigns diffs.GitsignsConfig|false
 ---@field committia diffs.CommittiaConfig|false
 ---@field telescope diffs.TelescopeConfig|false
@@ -77,6 +80,7 @@
 ---@field integrations diffs.IntegrationsConfig
 ---@field fugitive? diffs.FugitiveConfig|false deprecated: use integrations.fugitive
 ---@field neogit? diffs.NeogitConfig|false deprecated: use integrations.neogit
+---@field neojj? diffs.NeojjConfig|false deprecated: use integrations.neojj
 ---@field gitsigns? diffs.GitsignsConfig|false deprecated: use integrations.gitsigns
 ---@field committia? diffs.CommittiaConfig|false deprecated: use integrations.committia
 ---@field telescope? diffs.TelescopeConfig|false deprecated: use integrations.telescope
@@ -161,6 +165,7 @@ local default_config = {
   integrations = {
     fugitive = false,
     neogit = false,
+    neojj = false,
     gitsigns = false,
     committia = false,
     telescope = false,
@@ -239,6 +244,15 @@ function M.compute_filetypes(opts)
     table.insert(fts, 'NeogitCommitView')
     table.insert(fts, 'NeogitDiffView')
   end
+  local njj = intg.neojj
+  if njj == nil then
+    njj = opts.neojj
+  end
+  if njj == true or type(njj) == 'table' then
+    table.insert(fts, 'NeojjStatus')
+    table.insert(fts, 'NeojjCommitView')
+    table.insert(fts, 'NeojjDiffView')
+  end
   if type(opts.extra_filetypes) == 'table' then
     for _, ft in ipairs(opts.extra_filetypes) do
       table.insert(fts, ft)
@@ -610,7 +624,7 @@ local function compute_highlight_groups(is_default)
   end
 end
 
-local integration_keys = { 'fugitive', 'neogit', 'gitsigns', 'committia', 'telescope' }
+local integration_keys = { 'fugitive', 'neogit', 'neojj', 'gitsigns', 'committia', 'telescope' }
 
 local function migrate_integrations(opts)
   if opts.integrations then
@@ -674,6 +688,10 @@ local function init()
     intg.neogit = {}
   end
 
+  if intg.neojj == true then
+    intg.neojj = {}
+  end
+
   if intg.gitsigns == true then
     intg.gitsigns = {}
   end
@@ -1032,6 +1050,21 @@ function M.attach(bufnr)
     })
   end
 
+  local neojj_augroup = nil
+  if config.integrations.neojj and vim.bo[bufnr].filetype:match('^Neojj') then
+    vim.b[bufnr].neojj_disable_hunk_highlight = true
+    neojj_augroup = vim.api.nvim_create_augroup('diffs_neojj_' .. bufnr, { clear = true })
+    vim.api.nvim_create_autocmd('User', {
+      pattern = 'NeojjDiffLoaded',
+      group = neojj_augroup,
+      callback = function()
+        if vim.api.nvim_buf_is_valid(bufnr) and attached_buffers[bufnr] then
+          M.refresh(bufnr)
+        end
+      end,
+    })
+  end
+
   dbg('attaching to buffer %d', bufnr)
 
   ensure_cache(bufnr)
@@ -1045,6 +1078,9 @@ function M.attach(bufnr)
       if neogit_augroup then
         pcall(vim.api.nvim_del_augroup_by_id, neogit_augroup)
       end
+      if neojj_augroup then
+        pcall(vim.api.nvim_del_augroup_by_id, neojj_augroup)
+      end
     end,
   })
 end
@@ -1101,6 +1137,12 @@ function M.get_fugitive_config()
   return config.integrations.fugitive
 end
 
+---@return diffs.NeojjConfig|false
+function M.get_neojj_config()
+  init()
+  return config.integrations.neojj
+end
+
 ---@return diffs.CommittiaConfig|false
 function M.get_committia_config()
   init()

lua/diffs/parser.lua

@@ -129,6 +129,18 @@ local function get_repo_root(bufnr)
     return vim.fn.fnamemodify(neogit_git_dir, ':h')
   end
 
+  if vim.bo[bufnr].filetype:match('^Neojj') then
+    local jj_ok, jj_mod = pcall(require, 'neojj.lib.jj')
+    if jj_ok then
+      local rok, repo = pcall(function()
+        return jj_mod.repo
+      end)
+      if rok and repo and repo.worktree_root then
+        return repo.worktree_root
+      end
+    end
+  end
+
   local cwd = vim.fn.getcwd()
   local git = require('diffs.git')
   return git.get_repo_root(cwd .. '/.')
@@ -244,6 +256,10 @@ function M.parse_buffer(bufnr)
       or (not logical:match('^deleted file mode') and logical:match('^deleted%s+(.+)$'))
       or logical:match('^renamed%s+(.+)$')
       or logical:match('^copied%s+(.+)$')
+      or logical:match('^added%s+(.+)$')
+      or logical:match('^updated%s+(.+)$')
+      or logical:match('^changed%s+(.+)$')
+      or logical:match('^unmerged%s+(.+)$')
     local bare_file = not hunk_start and logical:match('^([^%s]+%.[^%s]+)$')
     local filename = logical:match('^[MADRCU%?!]%s+(.+)$')
       or diff_git_file

spec/neojj_integration_spec.lua

@@ -0,0 +1,173 @@
+require('spec.helpers')
+
+vim.g.diffs = { integrations = { neojj = 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('neojj_integration', function()
+  describe('neojj_disable_hunk_highlight', function()
+    it('sets neojj_disable_hunk_highlight on NeojjStatus 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', 'NeojjStatus', { buf = bufnr })
+      diffs.attach(bufnr)
+
+      assert.is_true(vim.b[bufnr].neojj_disable_hunk_highlight)
+
+      delete_buffer(bufnr)
+    end)
+
+    it('does not set neojj_disable_hunk_highlight on non-Neojj 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].neojj_disable_hunk_highlight)
+
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('NeojjStatus buffer attach', function()
+    it('populates hunk_cache for NeojjStatus 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', 'NeojjStatus', { 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 NeojjDiffView 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', 'NeojjDiffView', { 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 neojj patterns', function()
+    it('detects added prefix via parser', function()
+      local bufnr = create_buffer({
+        'added   utils.py',
+        '@@ -0,0 +1,2 @@',
+        '+def hello():',
+        '+    pass',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.equal('utils.py', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects updated prefix via parser', function()
+      local bufnr = create_buffer({
+        'updated   config.toml',
+        '@@ -1,2 +1,3 @@',
+        ' [section]',
+        '+key = "val"',
+        ' other = 1',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.equal('config.toml', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects changed prefix via parser', function()
+      local bufnr = create_buffer({
+        'changed   main.rs',
+        '@@ -1,1 +1,2 @@',
+        ' fn main() {}',
+        '+fn helper() {}',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+      assert.are.equal(1, #hunks)
+      assert.are.equal('main.rs', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('detects unmerged prefix via parser', function()
+      local bufnr = create_buffer({
+        'unmerged   conflict.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('conflict.lua', hunks[1].filename)
+      delete_buffer(bufnr)
+    end)
+
+    it('parses multi-file neojj buffer with modified and added', function()
+      local bufnr = create_buffer({
+        'modified   test.lua',
+        '@@ -1,2 +1,3 @@',
+        ' local M = {}',
+        '+local x = 1',
+        ' return M',
+        'added   utils.py',
+        '@@ -0,0 +1,2 @@',
+        '+def hello():',
+        '+    pass',
+      })
+      local hunks = parser.parse_buffer(bufnr)
+      assert.are.equal(2, #hunks)
+      assert.are.equal('test.lua', hunks[1].filename)
+      assert.are.equal('utils.py', hunks[2].filename)
+      delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('compute_filetypes', function()
+    it('includes Neojj filetypes when neojj integration is enabled', function()
+      local fts = diffs.compute_filetypes({ integrations = { neojj = true } })
+      assert.is_true(vim.tbl_contains(fts, 'NeojjStatus'))
+      assert.is_true(vim.tbl_contains(fts, 'NeojjCommitView'))
+      assert.is_true(vim.tbl_contains(fts, 'NeojjDiffView'))
+    end)
+
+    it('excludes Neojj filetypes when neojj integration is disabled', function()
+      local fts = diffs.compute_filetypes({ integrations = { neojj = false } })
+      assert.is_false(vim.tbl_contains(fts, 'NeojjStatus'))
+      assert.is_false(vim.tbl_contains(fts, 'NeojjCommitView'))
+      assert.is_false(vim.tbl_contains(fts, 'NeojjDiffView'))
+    end)
+  end)
+end)