Nothing should have overall help option

[pp-mo]

Currently "nothing" simply defaults to "nothing start", and "nothing --help" does the same.
It would be good to have an overall "--help" option listing commands,
and (I think) for that to be the default if you say nothing else.

[trexfeathers]

Wait, just thinking about this some more...

• What exactly is it that you want --help to do differently?
• Showing --help is already the default. What should be different?