GOption might need a tidbit more functionality as it is targeted to be used all
over the place instead of popt now.

I noticed that there is a lack of control over when the actual usage is displayed.

If this is by "design" in order to only show usage on -?/--help and imply that
the called application will return a warning/error for a specific wrong
argument, then please close this report. (Will report errors instead of usage to
the user)

Example:

void g_option_context_help_show[_and_exit?](GOptionContext *context,
GOptionGroup *group)

:)