test: skip relative config include across Windows drives

On Windows, the writable temporary directory and the checkout can be on
different drives. os.path.relpath() raises ValueError for such paths before
GitConfigParser is exercised.

Skip this relative-path-specific test on Windows, where the test setup cannot
reliably construct the required relative path.

Validation:
- pytest -q test/test_config.py
- ruff check test/test_config.py
- ruff format --check test/test_config.py

Author: codex

test/test_config.py

@@ -320,6 +320,9 @@ def test_config_relative_path_include(self, rw_dir):
         with GitConfigParser(config_path, read_only=False) as cw:
             cw.set_value("include", "path", "included")
 
+        if osp.splitdrive(config_path)[0] != osp.splitdrive(os.getcwd())[0]:
+            pytest.skip("The temporary directory and checkout are on different drives")
+
         relative_config_path = osp.relpath(config_path)
         with GitConfigParser(relative_config_path, read_only=True) as cr:
             assert cr.get_value("included", "value") == "included"