[feature] %(default)s should be replaced with action.default.

[Freed-Wu]

    parser.add_argument(
        '--color', default='auto',
        type=use_color,
        metavar='{' + ','.join(COLOR_CHOICES) + '}',
        help='Whether to use color in output.  Defaults to `%(default)s`.',
    )

should replace %(default)s as action.default.