-- | Specify a metavariable for the argument.
--
-- Metavariables have no effect on the actual parser, and only serve to specify
-- the symbolic name for an argument to be displayed in the help text.
metavar :: HasMetavar f => String -> Mod f a
metavar var = optionMod $ \p -> p { propMetaVar = var }
metavar :: HasMetavar f => String -> Mod f a
metavar var = optionMod $ \p -> p { propMetaVar = var }
metavar var = optionMod $ \p -> p { propMetaVar = var }