@unbare_repo
    def config_writer(self, index=None, write=True):
        writer = self._config_parser_constrained(read_only=False)
        if index is not None:
            writer.config._index = index
        writer.config._auto_write = write
        return writer
This is the mainline.
dataset/ETHPy150Open gitpython-developers/GitPython/git/objects/submodule/base.py/Submodule.config_writer--crossover with--dataset/ETHPy150Open aparo/pyes/contrib/mailman/archive_and_index.py/main