(defbitfield g-option-flags
  :none
  :hidden
  :in-main
  :reverse
  :no-arg
  :filename
  :optional-arg
  :noalias)  

:none

No flags.

:hidden

The option does not appear in --help output.

:in-main

The option appears in the main section of the --help output, even if it is defined in a group.

:reverse

For options of the :none kind, this flag indicates that the sense of the option is reversed.

:no-arg

For options of the :callback kind, this flag indicates that the callback function does not take any argument, like a :none option.

:filename

For options of the :callback kind, this flag indicates that the argument should be passed to the callback function in the GLib filename encoding rather than UTF-8.

:optional-arg

For options of the :callback kind, this flag indicates that the argument supply is optional. If no argument is given then data of the GOptionParseFunc callback function will be set to NULL.

:noalias

This flag turns off the automatic conflict resolution which prefixes long option names with a group name, if there is a conflict. This option should only be used in situations where aliasing is necessary to model some legacy command line interface. It is not safe to use this option, unless all option groups are under your direct control.