Treat gitignore segments of three or more asterisks as a globstar

CHANGES_1.in.rst

@@ -21,6 +21,7 @@ New features:
 
 Bug fixes:
 
+- A gitignore pattern segment made of three or more asterisks (e.g., `***/x`) is now treated as a double-asterisk, matching Git.
 - Hyperscan backend no longer fails on multibyte UTF-8 characters.
 - `Pull #123`_: Ignore invalid gitignore bracket ranges for `GitIgnoreSpec`.
 - `Pull #128`_: Support POSIX character classes (e.g. `[[:alpha:]]`) in gitignore bracket expressions.

pathspec/patterns/gitignore/base.py

@@ -102,6 +102,22 @@ def _strip_trailing_ws(pattern: str) -> str:
 	return pattern[:last_ws]
 
 
+def _collapse_star_runs(segments: list[str]) -> list[str]:
+	"""
+	Replace each pattern segment that consists only of three or more asterisks
+	(e.g., ``***``) with a double-asterisk (``**``). Git's wildmatch treats a run
+	of asterisks as a single globstar when it spans a whole path segment.
+
+	*segments* (:class:`list` of :class:`str`) are the pattern segments.
+
+	Returns the modified segments (:class:`list` of :class:`str`).
+	"""
+	return [
+		'**' if len(seg) > 2 and seg.count('*') == len(seg) else seg
+		for seg in segments
+	]
+
+
 def _sub_bracket_token(match: re.Match[str]) -> str:
 	"""
 	Translate a single token matched by :data:`_BRACKET_TOKEN_REGEX`. A token can

pathspec/patterns/gitignore/basic.py

@@ -23,6 +23,7 @@
 	_PosixClassError,
 	_RangeNotationError,
 	_TrailingBackslashError,
+	_collapse_star_runs,
 	_strip_trailing_ws)
 
 
@@ -221,7 +222,7 @@ def pattern_to_regex(
 			return (None, None)
 
 		# Split pattern into segments.
-		orig_segs = pattern_str.split('/')
+		orig_segs = _collapse_star_runs(pattern_str.split('/'))
 
 		# Check whether the pattern is specifically a directory pattern before
 		# normalization.

pathspec/patterns/gitignore/spec.py

@@ -25,6 +25,7 @@
 	_PosixClassError,
 	_RangeNotationError,
 	_TrailingBackslashError,
+	_collapse_star_runs,
 	_strip_trailing_ws)
 
 _DIR_MARK = 'ps_d'
@@ -265,7 +266,7 @@ def pattern_to_regex(
 			return (None, None)
 
 		# Split pattern into segments.
-		orig_segs = pattern_str.split('/')
+		orig_segs = _collapse_star_runs(pattern_str.split('/'))
 
 		# Check whether the pattern is specifically a directory pattern before
 		# normalization.

tests/test_10_gitignore_star_runs.py

@@ -0,0 +1,54 @@
+"""
+Test runs of three or more asterisks that span a whole gitignore path segment.
+"""
+
+import unittest
+
+from pathspec import GitIgnoreSpec
+from pathspec.patterns.gitignore.basic import GitIgnoreBasicPattern
+from pathspec.patterns.gitignore.spec import GitIgnoreSpecPattern
+
+# Each case is (pattern, paths that Git matches, paths that Git does not match).
+# Git's wildmatch treats a run of asterisks that spans a whole path segment as
+# a single globstar (``**``).
+CASES = (
+	('***/x', ('x', 'a/x', 'a/b/x'), ('xx', 'a/xx')),
+	('****/x', ('x', 'a/x', 'a/b/x'), ('xx',)),
+	('a/***', ('a/b', 'a/b/c'), ('a', 'b/a', 'b/a/c')),
+	('a/***/b', ('a/b', 'a/x/b', 'a/x/y/b'), ('a/x', 'b/x/b')),
+	('***', ('a', 'a/b', 'a/b/c'), ()),
+	# A run of asterisks inside a segment is still a single asterisk.
+	('a***b', ('ab', 'axxb'), ('a/b', 'a/x/b')),
+)
+
+
+class StarRunTest(unittest.TestCase):
+	"""
+	The :class:`StarRunTest` class tests asterisk runs against Git's behavior.
+	"""
+
+	def test_pattern_classes(self):
+		"""
+		Tests that both gitignore pattern classes treat a segment of asterisks
+		like a double-asterisk.
+		"""
+		for factory in (GitIgnoreBasicPattern, GitIgnoreSpecPattern):
+			for line, matches, misses in CASES:
+				with self.subTest(factory=factory.__name__, line=line):
+					pattern = factory(line)
+					for path in matches:
+						self.assertTrue(pattern.match_file(path), path)
+					for path in misses:
+						self.assertFalse(pattern.match_file(path), path)
+
+	def test_gitignore_spec(self):
+		"""
+		Tests that :class:`.GitIgnoreSpec` matches the same paths as Git.
+		"""
+		for line, matches, misses in CASES:
+			with self.subTest(line=line):
+				spec = GitIgnoreSpec.from_lines([line])
+				for path in matches:
+					self.assertTrue(spec.match_file(path), path)
+				for path in misses:
+					self.assertFalse(spec.match_file(path), path)