Dec 7, 2025 · Dec 8, 2025 · Dec 9, 2025 · Dec 8, 2025
diff --git a/git/diff.py b/git/diff.py
    path = _octal_byte_re.sub(_octal_repl, path)

    if has_ab_prefix:
        assert path.startswith(b"a/") or path.startswith(b"b/")
        # Support standard (a/b) and mnemonicPrefix (c/w/i/o/h) prefixes
        # See git-config diff.mnemonicPrefix documentation
        valid_prefixes = (b"a/", b"b/", b"c/", b"w/", b"i/", b"o/", b"h/")
        assert any(path.startswith(p) for p in valid_prefixes), f"Unexpected path prefix: {path[:10]!r}"
        path = path[2:]

    return path
    """

    # Precompiled regex.
    # Note: The path prefixes support both default (a/b) and mnemonicPrefix mode
    # which can use prefixes like c/ (commit), w/ (worktree), i/ (index), o/ (object), and h/ (HEAD)
    re_header = re.compile(
        rb"""
                                ^diff[ ]--git
                                    [ ](?P<a_path_fallback>"?[ab]/.+?"?)[ ](?P<b_path_fallback>"?[ab]/.+?"?)\n
                                    [ ](?P<a_path_fallback>"?[abciwoh]/.+?"?)[ ](?P<b_path_fallback>"?[abciwoh]/.+?"?)\n
                                (?:^old[ ]mode[ ](?P<old_mode>\d+)\n
                                   ^new[ ]mode[ ](?P<new_mode>\d+)(?:\n|$))?
                                (?:^similarity[ ]index[ ]\d+%\n
diff --git a/test/test_diff.py b/test/test_diff.py
        self.assertEqual(res[13].a_path, 'a/"with-quotes"')
        self.assertEqual(res[13].b_path, 'b/"with even more quotes"')

    def test_diff_mnemonic_prefix(self):
        """Test that diff parsing works with mnemonicPrefix enabled.

        When diff.mnemonicPrefix=true is set in git config, git uses different
        prefixes for diff paths:
        - c/ for commit
        - w/ for worktree
        - i/ for index
        - o/ for object
        - h/ for HEAD

        This addresses issue #2013 where the regex only matched [ab]/ prefixes.
        """
        # Test all mnemonicPrefix combinations
        # Each tuple is (a_prefix, b_prefix) representing different comparison types
        prefix_pairs = [
            (b"c/", b"w/"),  # commit vs worktree
            (b"c/", b"i/"),  # commit vs index
            (b"i/", b"w/"),  # index vs worktree
            (b"o/", b"w/"),  # object vs worktree
            (b"h/", b"i/"),  # HEAD vs index
            (b"h/", b"w/"),  # HEAD vs worktree
        ]

        for a_prefix, b_prefix in prefix_pairs:
            with self.subTest(a_prefix=a_prefix, b_prefix=b_prefix):
                diff_mnemonic = (
                    b"diff --git " + a_prefix + b".vscode/launch.json " + b_prefix + b".vscode/launch.json\n"
                    b"index 1234567890abcdef1234567890abcdef12345678.."
                    b"abcdef1234567890abcdef1234567890abcdef12 100644\n"
                    b"--- " + a_prefix + b".vscode/launch.json\n"
                    b"+++ " + b_prefix + b".vscode/launch.json\n"
                    b"@@ -1,3 +1,3 @@\n"
                    b"-old content\n"
                    b"+new content\n"
                )
                diff_proc = StringProcessAdapter(diff_mnemonic)
                diffs = Diff._index_from_patch_format(self.rorepo, diff_proc)

                # Should parse successfully (previously would fail or return empty)
                self.assertEqual(len(diffs), 1)
                diff = diffs[0]
                # The path should be extracted correctly (without the prefix)
                self.assertEqual(diff.a_path, ".vscode/launch.json")
                self.assertEqual(diff.b_path, ".vscode/launch.json")

    def test_diff_patch_format(self):
        # Test all of the 'old' format diffs for completeness - it should at least be
        # able to deal with it.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -113,7 +113,10 @@ def decode_path(path: bytes, has_ab_prefix: bool = True) -> Optional[bytes]:
		path = _octal_byte_re.sub(_octal_repl, path)

		if has_ab_prefix:
		assert path.startswith(b"a/") or path.startswith(b"b/")
		# Support standard (a/b) and mnemonicPrefix (c/w/i/o/h) prefixes
		# See git-config diff.mnemonicPrefix documentation
		valid_prefixes = (b"a/", b"b/", b"c/", b"w/", b"i/", b"o/", b"h/")
		assert any(path.startswith(p) for p in valid_prefixes), f"Unexpected path prefix: {path[:10]!r}"
		path = path[2:]

		return path
Expand DownExpand Up		@@ -367,10 +370,12 @@ class Diff:
		"""

		# Precompiled regex.
		# Note: The path prefixes support both default (a/b) and mnemonicPrefix mode
		# which can use prefixes like c/ (commit), w/ (worktree), i/ (index), o/ (object), and h/ (HEAD)
		re_header = re.compile(
		rb"""
		^diff[ ]--git
		[ ](?P<a_path_fallback>"?[ab]/.+?"?)[ ](?P<b_path_fallback>"?[ab]/.+?"?)\n
		[ ](?P<a_path_fallback>"?[abciwoh]/.+?"?)[ ](?P<b_path_fallback>"?[abciwoh]/.+?"?)\n
		(?:^old[ ]mode[ ](?P<old_mode>\d+)\n
		^new[ ]mode[ ](?P<new_mode>\d+)(?:\n\|$))?
		(?:^similarity[ ]index[ ]\d+%\n
Expand Down