Recognize UNC roots on older Python versions

Author: Byron

git/util.py

@@ -326,7 +326,7 @@ def _is_path_rooted(path: PathLike) -> bool:
     """
     drive, tail = osp.splitdrive(os.fspath(path))
     separators = (os.sep,) if os.altsep is None else (os.sep, os.altsep)
-    return tail.startswith(separators) or bool(drive) and osp.isabs(path)
+    return tail.startswith(separators) or drive.startswith(separators)
 
 
 def _to_relative_path(root: PathLike, path: PathLike) -> str: