Preserve POSIX backslashes in include patterns

Author: Byron

git/config.py

@@ -576,8 +576,11 @@ def _all_items(section: str) -> List[Tuple[str, str]]:
             value = match.group(2).strip()
 
             if keyword in ["gitdir", "gitdir/i"]:
-                value = osp.expanduser(value).replace("\\", "/")
-                git_dir = os.fspath(self._repo.git_dir).replace("\\", "/") if self._repo.git_dir else None
+                value = osp.expanduser(value)
+                git_dir = os.fspath(self._repo.git_dir) if self._repo.git_dir else None
+                if sys.platform == "win32":
+                    value = value.replace("\\", "/")
+                    git_dir = git_dir.replace("\\", "/") if git_dir else None
 
                 drive, _tail = osp.splitdrive(value)
                 if not drive and not any(value.startswith(s) for s in ["./", "/"]):

test/test_config.py

@@ -7,6 +7,7 @@
 import io
 import os
 import os.path as osp
+import sys
 from unittest import mock
 
 import pytest
@@ -501,6 +502,22 @@ def test_conditional_includes_from_git_dir(self, rw_dir):
             assert config._has_includes()
             assert config._included_paths() == [("path", path2)]
 
+    @pytest.mark.skipif(sys.platform == "win32", reason="Backslashes are path separators on Windows.")
+    @with_rw_directory
+    def test_conditional_includes_preserve_posix_backslashes(self, rw_dir):
+        git_dir = osp.join(rw_dir, "target", "repo")
+        repo = mock.Mock(git_dir=git_dir)
+        config_path = osp.join(rw_dir, "config")
+        included_path = osp.join(rw_dir, "included")
+        pattern = git_dir.replace("/target/repo", R"/target\repo")
+
+        with open(config_path, "w") as stream:
+            stream.write(f'[includeIf "gitdir:{pattern}"]\n    path={included_path}\n')
+
+        with GitConfigParser(config_path, repo=repo) as config:
+            assert config._has_includes()
+            assert config._included_paths() == []
+
     @with_rw_directory
     def test_conditional_includes_from_branch_name(self, rw_dir):
         # Initiate mocked branch.