Support dash-separated names

[jaraco]

I recently tried:

@autocommand
def main(dry_run=False):
  ...

And it created an option --dry_run, which was a surprised because other parts of autocommand seem to use - as the separator (e.g. --no- for negation).

It would be nice if there were an option to substitute the underscore for a dash, e.g.

@autocommand(preferred_separator='-')
def main(dry_run=False):
  ...

Would then expect --dry-run and --no-dry-run as the options.

[Lucretiel]

This has been on my list for a while! When I first designed it, I actually deliberately wanted the no- vs _ behavior, because it mean there wasn't any possibility of a name collision. I've since come to the pretty obvious conclusion that that's not worth worrying about. Thanks for the ticket.