def refresh(cls) -> Literal[True]:
        """Update information about which :manpage:`git-fetch(1)` flags are supported
        by the git executable being used.

        Called by the :func:`git.refresh` function in the top level ``__init__``.
        """
        # Clear the old values in _flag_map.
        with contextlib.suppress(KeyError):
            del cls._flag_map["t"]
        with contextlib.suppress(KeyError):
            del cls._flag_map["-"]

        # Set the value given the git version.
        if Git().version_info[:2] >= (2, 10):
            cls._flag_map["t"] = cls.TAG_UPDATE
        else:
            cls._flag_map["-"] = cls.TAG_UPDATE

        return True
Update information about which :manpage:`git-fetch(1)` flags are supported
        by the git executable being used.

        Called by the :func:`git.refresh` function in the top level ``__init__``.
        
git/remote.py