Support for negative numbers

[thomask77]

I would like to re-open the discussion from issue #555 and #1624.

My program makes heavy use of numeric arguments, including negative numbers, special float values (NaN, Infinity..), negative hex numbers, etc.

At the moment I'm using the following monkey patch as a work-around:

from click.parser import OptionParser, ParsingState


def _is_number(arg: str) -> bool:
    try:
        _ = int(arg, 0)
    except ValueError:
        try:
            _ = float(arg)
        except ValueError:
            return False
    return True


# Allow negative numbers as arguments
#
# Based on click/parser.py v8.1.7
#
def _process_args_for_options(self, state: ParsingState) -> None:
    while state.rargs:
        arg = state.rargs.pop(0)
        if arg == "--":
            return
        elif arg[:1] in self._opt_prefixes and len(arg) > 1 and not _is_number(arg):
            self._process_opts(arg, state)
        elif self.allow_interspersed_args:
            state.largs.append(arg)
        else:
            state.rargs.insert(0, arg)
            return


# Monkey-patch the OptionParser class
#
OptionParser._process_args_for_options = _process_args_for_options

It would be nice, if click would offer an official mode that accepts negative numbers.
I can also submit a PR, but would need further input on how to properly integrate the feature.