test(fugitive): add unit tests for line parsing

Tests for get_section_at_line() and get_file_at_line() covering:
- Section detection (staged, unstaged, untracked)
- File parsing (modified, added, deleted, renamed, untracked)
- Hunk line walk-back to parent file
- Files appearing in multiple sections

spec/fugitive_spec.lua

@@ -0,0 +1,177 @@
+require('spec.helpers')
+
+local fugitive = require('diffs.fugitive')
+
+describe('fugitive', function()
+  describe('get_section_at_line', function()
+    local function create_status_buffer(lines)
+      local buf = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+      return buf
+    end
+
+    it('returns staged for lines in Staged section', function()
+      local buf = create_status_buffer({
+        'Head: main',
+        '',
+        'Staged (2)',
+        'M  file1.lua',
+        'A  file2.lua',
+        '',
+        'Unstaged (1)',
+        'M  file3.lua',
+      })
+      assert.equals('staged', fugitive.get_section_at_line(buf, 4))
+      assert.equals('staged', fugitive.get_section_at_line(buf, 5))
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('returns unstaged for lines in Unstaged section', function()
+      local buf = create_status_buffer({
+        'Head: main',
+        '',
+        'Staged (1)',
+        'M  file1.lua',
+        '',
+        'Unstaged (2)',
+        'M  file2.lua',
+        'M  file3.lua',
+      })
+      assert.equals('unstaged', fugitive.get_section_at_line(buf, 7))
+      assert.equals('unstaged', fugitive.get_section_at_line(buf, 8))
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('returns untracked for lines in Untracked section', function()
+      local buf = create_status_buffer({
+        'Head: main',
+        '',
+        'Untracked (2)',
+        '?  newfile.lua',
+        '?  another.lua',
+      })
+      assert.equals('untracked', fugitive.get_section_at_line(buf, 4))
+      assert.equals('untracked', fugitive.get_section_at_line(buf, 5))
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('returns nil for lines before any section', function()
+      local buf = create_status_buffer({
+        'Head: main',
+        'Push: origin/main',
+        '',
+        'Staged (1)',
+        'M  file1.lua',
+      })
+      assert.is_nil(fugitive.get_section_at_line(buf, 1))
+      assert.is_nil(fugitive.get_section_at_line(buf, 2))
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+  end)
+
+  describe('get_file_at_line', function()
+    local function create_status_buffer(lines)
+      local buf = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+      return buf
+    end
+
+    it('parses simple modified file', function()
+      local buf = create_status_buffer({
+        'Unstaged (1)',
+        'M  src/foo.lua',
+      })
+      local filename, section = fugitive.get_file_at_line(buf, 2)
+      assert.equals('src/foo.lua', filename)
+      assert.equals('unstaged', section)
+      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 new name', function()
+      local buf = create_status_buffer({
+        'Staged (1)',
+        'R  oldname.lua -> newname.lua',
+      })
+      local filename, section = fugitive.get_file_at_line(buf, 2)
+      assert.equals('newname.lua', filename)
+      assert.equals('staged', section)
+      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)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('returns nil for section header', function()
+      local buf = create_status_buffer({
+        'Unstaged (1)',
+        'M  file.lua',
+      })
+      local filename, section = fugitive.get_file_at_line(buf, 1)
+      assert.is_nil(filename)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('walks back from hunk line to find file', function()
+      local buf = create_status_buffer({
+        'Unstaged (1)',
+        'M  file.lua',
+        '@@ -1,3 +1,4 @@',
+        ' local M = {}',
+        '+local new = true',
+        ' return M',
+      })
+      local filename, section = fugitive.get_file_at_line(buf, 5)
+      assert.equals('file.lua', filename)
+      assert.equals('unstaged', section)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+
+    it('handles file with both staged and unstaged indicator', function()
+      local buf = create_status_buffer({
+        'Staged (1)',
+        'M  both.lua',
+        '',
+        'Unstaged (1)',
+        'M  both.lua',
+      })
+      local filename1, section1 = fugitive.get_file_at_line(buf, 2)
+      assert.equals('both.lua', filename1)
+      assert.equals('staged', section1)
+
+      local filename2, section2 = fugitive.get_file_at_line(buf, 5)
+      assert.equals('both.lua', filename2)
+      assert.equals('unstaged', section2)
+      vim.api.nvim_buf_delete(buf, { force = true })
+    end)
+  end)
+end)