create alias unbuttoned_pants -> open_fly
Both tags are used in exactly the same way. I don't see how anyone can justify maintaining a more specific "unbuttoned_*" tag if it routinely gets used for posts where there are no visible buttons. It makes more sense to use the broader open_fly and let people add unbuttoned as well wherever it applies.
EDIT: The tag alias unbuttoned_pants -> open_fly (forum #153069) has been approved by @NWF_Renim.
Updated by DanbooruBot