def __init__(self, working_dir: Union[None, PathLike] = None) -> None:
        """Initialize this instance with:

        :param working_dir:
            Git directory we should work in. If ``None``, we always work in the current
            directory as returned by :func:`os.getcwd`.
            This is meant to be the working tree directory if available, or the
            ``.git`` directory in case of bare repositories.
        """
        super().__init__()
        self._working_dir = expand_path(working_dir)
        self._git_options: Union[List[str], Tuple[str, ...]] = ()
        self._persistent_git_options: List[str] = []

        # Extra environment variables to pass to git commands
        self._environment: Dict[str, str] = {}

        # Cached version slots
        self._version_info: Union[Tuple[int, ...], None] = None
        self._version_info_token: object = None

        # Cached command slots
        self.cat_file_header: Union[None, TBD] = None
        self.cat_file_all: Union[None, TBD] = None
Initialize this instance with:

        :param working_dir:
            Git directory we should work in. If ``None``, we always work in the current
            directory as returned by :func:`os.getcwd`.
            This is meant to be the working tree directory if available, or the
            ``.git`` directory in case of bare repositories.
        
git/cmd.py