def _envdir_merge_func(command_args, noxfile_args):
    """Ensure that there is always some envdir.

    Args:
        command_args (_option_set.Namespace): The options specified on the
            command-line.
        noxfile_Args (_option_set.Namespace): The options specified in the
            Noxfile.
    """
    return command_args.envdir or noxfile_args.envdir or '.nox'
