def arg(*args, **kwargs):
    """Decorator for CLI args.

    Example:

    >>> @arg("name", help="Name of the new entity")
    ... def entity_create(args):
    ...     pass
    """
    def _decorator(func):
        add_arg(func, *args, **kwargs)
        return func
    return _decorator


def add_arg(func, *args, **kwargs):
    """Bind CLI arguments to a shell.py `do_foo` function."""

    if not hasattr(func, 'arguments'):
        func.arguments = []

    # NOTE(sirp): avoid dups that can occur when the module is shared across
    # tests.
    if (args, kwargs) not in func.arguments:
        # Because of the semantics of decorator composition if we just append
        # to the options list positional options will appear to be backwards.
        func.arguments.insert(0, (args, kwargs))