try to fix pygbag failing when --help passed

[wade-cheng]

pygbag errors with codes 89 and 83 when called with just --help.

$ pygbag --help
89: Error, Last argument must be a valid app top level directory, or the main.py python script
83: Error, no main.py .../--help/main.py found in folder
89: missing requirement(s)

This may be confusing. Command line programs usually do not fail when called with just --help, even if they usually require other arguments on standard runs. To get --help to work with pygbag, one must use it alongside a valid argument, which the user may not know how to choose without the help text. Catch-22!

I did some digging, and pygbag first processes args with set_args, failing if the app folder or other metadata could not be found. Then, it calls main_run. This means if we create our parser in main_run, we will fail even if we just run pygbag --help. Thus, I created a get_parser function that can be called with get_parser(None, None, None, None) in set_args when --help is in the command line arguments, to parse it to print out help data and then exit.

This might work, but might not. I didn't figure out how to run pygbag locally, so the coding was done a bit blind.

[pmp-p]

when no param is given, i had the silly idea to make a Textual interface to pick folder and select a file as main.py ( even if it is not named main.py), also check what modules to package with the game and a generic options editor which could build upon the pygbag.ini

when i give up on the idea merging will be obvious, thanks for the effort and the patience.

[wade-cheng]

quite embarrasingly, I forgot to check the issue tracker, where #96 mentions this.

(also, I feel the need to state again that this is a really conceptual pr and very well could be bugged and breaks everything haha. Though, I was fairly sure that if bugged, it becomes sound after a little bugfixing.)

[pmp-p]

what if --help without script sent usage , and add '--help <folder/main.py>' to usage ?
and yeah check that it work with all exotic OS entrypoints ( ie mac/win )