module Action:sig..end
type 'a t
'accum-mutating action to perform when processing a flagval noarg : ('a -> unit) -> 'a tval arg : ('a -> string -> unit) -> 'a tval rest : ('a -> string list -> unit) -> 'a tval of_type : 'a Command.Flag.Type.t -> ('b -> 'a -> unit) -> 'b t