option with specific choices list

[Veratil]

I don't see any mention of this in the docs, but it would be nice to mimic the choices parameter as seen in the python argparse module (https://docs.python.org/dev/library/argparse.html#choices).

[mpeterv]

This is a good idea. Python's argparse accepts any value that has in operator as choices parameter, but in Lua it makes sense to support only arrays, at first at least. I'll try to implement this when I have time, in the meantime pull requests are welcome.

[nwf]

FWIW, this is implemented in the luarocks branch of this repository, at https://github.com/luarocks/argparse, in https://github.com/luarocks/argparse/pull/3/commits/dcd5162710fcc7f354ffa5eaed574e0cd6f03d06 in particular.