I think the `re.compile(r'^-.+$')` behavior could be better achieved by inserting a simple test in `_parse_optional` before the `_negative_number_matcher` test.

    # behave more like optparse even if the argument looks like a option
    if self.args_default_to_positional:
        return None

In effect, if the string does not match an action string, say it is a positional.

Making this patch to argparse.py is simple. How much to test it, and how document it requires more thought.