* PARSE_OPT_NONEG: says that this option cannot be negated
* PARSE_OPT_HIDDEN: this option is skipped in the default usage, and
* shown only in the full usage.
* PARSE_OPT_NONEG: says that this option cannot be negated
* PARSE_OPT_HIDDEN: this option is skipped in the default usage, and
* shown only in the full usage.