Ethan Sommer authored Nov 03, 2019 and Allan McRae committed Nov 04, 2019

Adds a "?" suffix that can be used to indicate that an option's argument is
optional.

This allows options to have a default behaviour when the user doesn't
specify one, e.g.: --color=[when] being able to behave like --color=auto
when only --color is passed

Options with optional arguments given on the command line will be returned
in the form "--opt=optarg" and "-o=optarg". Despite that not being the
syntax for passing an argument with a shortopt (trying to pass -o=foo
would make -o's argument "=foo"), this is done to allow the caller to split
the option and its optarg easily

Signed-off-by: Ethan Sommer <e5ten.arch@gmail.com>
Reviewed-by: Dave Reisner <dreisner@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>