It seems that registering cli opt after the original ConfigOpts is parsed is meaningless. So I think it would make more sense to throw an exception if the registered opt is an unknown opt, otherwise, it should behave similar to import_opt() when registering a known opt.
It seems that registering cli opt after the original ConfigOpts is parsed is meaningless. So I think it would make more sense to throw an exception if the registered opt is an unknown opt, otherwise, it should behave similar to import_opt() when registering a known opt.