def arg_default(*args, **kwargs):
    """Return default argument value as given by argparse's add_argument().

    The argument is passed through a mocked-up argument parser. This way, we
    get default parameters even if the feature is called directly and not
    through the CLI.
    """
    parser = argparse.ArgumentParser()
    parser.add_argument(*args, **kwargs)
    args = vars(parser.parse_args([]))
    _, default = args.popitem()
    return default