Fix gitignore pattern scoping bug for **/pattern in subdirectories

Previously, when a subdirectory .gitignore file contained patterns starting
with "**/", these patterns were incorrectly applied globally instead of being
scoped to that subdirectory's tree.

For example, if foo/.gitignore contained "**/test.txt", it would incorrectly
ignore test.txt files everywhere in the repository, including at the root
level and in other subdirectories like bar/test.txt.

The bug was in _parse_gitignore_content() where patterns starting with "**/"
were left unchanged (line 228: adjusted_pattern = line), making them global
instead of scoped.

Fixed by ensuring that even "**/pattern" gets the subdirectory prefix:
- Before: "**/test.txt" → "**/test.txt" (global)
- After: "**/test.txt" → "foo/**/test.txt" (scoped to foo/ subtree)

Added comprehensive test cases covering all gitignore pattern scenarios:
- Non-anchored patterns (foo.txt) - already worked correctly
- Anchored patterns (/foo.txt) - already worked correctly
- Double-star patterns (**/foo.txt) - was broken, now fixed
- Anchored double-star (/**/foo.txt) - already worked correctly

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/serena/util/file_system.py

@@ -225,7 +225,8 @@ class GitignoreParser:
                     # Non-anchored patterns can match anywhere below the gitignore directory
                     # We need to preserve this behavior
                     if line.startswith("**/"):
-                        adjusted_pattern = line
+                        # Even if pattern starts with **, it should still be scoped to the subdirectory
+                        adjusted_pattern = os.path.join(rel_dir, line)
                     else:
                         # Add the directory prefix but also allow matching in subdirectories
                         adjusted_pattern = os.path.join(rel_dir, "**", line)

test/serena/util/test_file_system.py

@@ -587,3 +587,122 @@ src/*.o
 
         # Note: Negation patterns in pathspec work differently than in git
         # This is a limitation of the pathspec library
+
+    def test_subdirectory_gitignore_pattern_scoping(self):
+        """Test that subdirectory .gitignore patterns are scoped correctly."""
+        # Create test structure: foo/ with subdirectory bar/
+        test_dir = self.repo_path / "test_subdir_scoping"
+        test_dir.mkdir()
+        (test_dir / "foo").mkdir()
+        (test_dir / "foo" / "bar").mkdir()
+
+        # Create files in various locations
+        (test_dir / "foo.txt").touch()  # root level
+        (test_dir / "foo" / "foo.txt").touch()  # in foo/
+        (test_dir / "foo" / "bar" / "foo.txt").touch()  # in foo/bar/
+
+        # Test case 1: foo.txt in foo/.gitignore should only ignore in foo/ subtree
+        gitignore = test_dir / "foo" / ".gitignore"
+        gitignore.write_text("foo.txt\n")
+
+        parser = GitignoreParser(str(test_dir))
+
+        # foo.txt at root should NOT be ignored by foo/.gitignore
+        assert not parser.should_ignore("foo.txt"), "Root foo.txt should not be ignored by foo/.gitignore"
+
+        # foo.txt in foo/ should be ignored
+        assert parser.should_ignore("foo/foo.txt"), "foo/foo.txt should be ignored"
+
+        # foo.txt in foo/bar/ should be ignored (within foo/ subtree)
+        assert parser.should_ignore("foo/bar/foo.txt"), "foo/bar/foo.txt should be ignored"
+
+    def test_anchored_pattern_in_subdirectory(self):
+        """Test that anchored patterns in subdirectory only match immediate children."""
+        test_dir = self.repo_path / "test_anchored_subdir"
+        test_dir.mkdir()
+        (test_dir / "foo").mkdir()
+        (test_dir / "foo" / "bar").mkdir()
+
+        # Create files
+        (test_dir / "foo.txt").touch()  # root level
+        (test_dir / "foo" / "foo.txt").touch()  # in foo/
+        (test_dir / "foo" / "bar" / "foo.txt").touch()  # in foo/bar/
+
+        # Test case 2: /foo.txt in foo/.gitignore should only match foo/foo.txt
+        gitignore = test_dir / "foo" / ".gitignore"
+        gitignore.write_text("/foo.txt\n")
+
+        parser = GitignoreParser(str(test_dir))
+
+        # foo.txt at root should NOT be ignored
+        assert not parser.should_ignore("foo.txt"), "Root foo.txt should not be ignored"
+
+        # foo.txt directly in foo/ should be ignored
+        assert parser.should_ignore("foo/foo.txt"), "foo/foo.txt should be ignored by /foo.txt pattern"
+
+        # foo.txt in foo/bar/ should NOT be ignored (anchored pattern only matches immediate children)
+        assert not parser.should_ignore("foo/bar/foo.txt"), "foo/bar/foo.txt should NOT be ignored by /foo.txt pattern"
+
+    def test_double_star_pattern_scoping(self):
+        """Test that **/pattern in subdirectory only applies within that subtree."""
+        test_dir = self.repo_path / "test_doublestar_scope"
+        test_dir.mkdir()
+        (test_dir / "foo").mkdir()
+        (test_dir / "foo" / "bar").mkdir()
+        (test_dir / "other").mkdir()
+
+        # Create files
+        (test_dir / "foo.txt").touch()  # root level
+        (test_dir / "foo" / "foo.txt").touch()  # in foo/
+        (test_dir / "foo" / "bar" / "foo.txt").touch()  # in foo/bar/
+        (test_dir / "other" / "foo.txt").touch()  # in other/
+
+        # Test case 3: **/foo.txt in foo/.gitignore should only ignore within foo/ subtree
+        gitignore = test_dir / "foo" / ".gitignore"
+        gitignore.write_text("**/foo.txt\n")
+
+        parser = GitignoreParser(str(test_dir))
+
+        # foo.txt at root should NOT be ignored
+        assert not parser.should_ignore("foo.txt"), "Root foo.txt should not be ignored by foo/.gitignore"
+
+        # foo.txt in foo/ should be ignored
+        assert parser.should_ignore("foo/foo.txt"), "foo/foo.txt should be ignored"
+
+        # foo.txt in foo/bar/ should be ignored (within foo/ subtree)
+        assert parser.should_ignore("foo/bar/foo.txt"), "foo/bar/foo.txt should be ignored"
+
+        # foo.txt in other/ should NOT be ignored (outside foo/ subtree)
+        assert not parser.should_ignore("other/foo.txt"), "other/foo.txt should NOT be ignored by foo/.gitignore"
+
+    def test_anchored_double_star_pattern(self):
+        """Test that /**/pattern in subdirectory works correctly."""
+        test_dir = self.repo_path / "test_anchored_doublestar"
+        test_dir.mkdir()
+        (test_dir / "foo").mkdir()
+        (test_dir / "foo" / "bar").mkdir()
+        (test_dir / "other").mkdir()
+
+        # Create files
+        (test_dir / "foo.txt").touch()  # root level
+        (test_dir / "foo" / "foo.txt").touch()  # in foo/
+        (test_dir / "foo" / "bar" / "foo.txt").touch()  # in foo/bar/
+        (test_dir / "other" / "foo.txt").touch()  # in other/
+
+        # Test case 4: /**/foo.txt in foo/.gitignore should correctly ignore only within foo/ subtree
+        gitignore = test_dir / "foo" / ".gitignore"
+        gitignore.write_text("/**/foo.txt\n")
+
+        parser = GitignoreParser(str(test_dir))
+
+        # foo.txt at root should NOT be ignored
+        assert not parser.should_ignore("foo.txt"), "Root foo.txt should not be ignored"
+
+        # foo.txt in foo/ should be ignored
+        assert parser.should_ignore("foo/foo.txt"), "foo/foo.txt should be ignored"
+
+        # foo.txt in foo/bar/ should be ignored (within foo/ subtree)
+        assert parser.should_ignore("foo/bar/foo.txt"), "foo/bar/foo.txt should be ignored"
+
+        # foo.txt in other/ should NOT be ignored (outside foo/ subtree)
+        assert not parser.should_ignore("other/foo.txt"), "other/foo.txt should NOT be ignored by foo/.gitignore"