Mark test_conditional_includes_from_git_dir xfail on Windows

As noted, the second of the config._included_paths() assertions
fails, which is in the "Ensure that config is included if path is
matching git_dir" sub-case.

It is returning 0 on Windows. THe GitConfigParser._has_includes
function returns the expression:

    self._merge_includes and len(self._included_paths())

Since _merge_includes is a bool, it appears the first branch of the
"and" is True, but then _included_paths returns an empty list.

Author: EliahKagan

Diff for: test/test_config.py

@@ -6,19 +6,15 @@
 import glob
 import io
 import os
+import os.path as osp
 from unittest import mock
 
+import pytest
+
 from git import GitConfigParser
 from git.config import _OMD, cp
-from test.lib import (
-    TestCase,
-    fixture_path,
-    SkipTest,
-)
-from test.lib import with_rw_directory
-
-import os.path as osp
 from git.util import rmfile
+from test.lib import SkipTest, TestCase, fixture_path, with_rw_directory
 
 
 _tc_lock_fpaths = osp.join(osp.dirname(__file__), "fixtures/*.lock")
@@ -239,6 +235,11 @@ def check_test_value(cr, value):
         with GitConfigParser(fpa, read_only=True) as cr:
             check_test_value(cr, tv)
 
+    @pytest.mark.xfail(
+        os.name == "nt",
+        reason='Second config._has_includes() assertion fails (for "config is included if path is matching git_dir")',
+        raises=AssertionError,
+    )
     @with_rw_directory
     def test_conditional_includes_from_git_dir(self, rw_dir):
         # Initiate repository path.