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fix(highlight): support combined diff format for unmerged files

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Problem: fugitive shows combined diffs (@@@ headers, 2-char prefixes)
for unmerged (UU) files. The parser and highlight pipeline assumed
unified diff format (@@, 1-char prefix), causing broken prefix
concealment, missing background colors on ` +`/`+ ` lines, and no
treesitter highlights due to garbage prefix chars in code arrays.

Solution: detect prefix width from the number of leading @ signs in
hunk headers. Propagate prefix_width through the parser (new field on
diffs.Hunk) and highlight pipeline (prefix stripping, col_offset,
concealment, line classification). Add U to filename pattern for
unmerged file detection. Skip intra-line diffing for combined diffs
since the 2-char prefix semantics don't produce meaningful change
groups.
This commit is contained in:
Barrett Ruth 2026-02-09 17:03:17 -05:00
parent 59fcf14817
commit a6dd0503b3
4 changed files with 232 additions and 29 deletions
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75
spec/parser_spec.lua
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@ -425,6 +425,81 @@ 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 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('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)
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('stores repo_root on hunk when available', function()
local bufnr = create_buffer({
'M lua/test.lua',