EnumSourceMap a constructor name to a command-line string: downcase the name and convert _ to -.
type ('a, 'b) make_param =
?represent_choice_with:string ->
?aliases:string list ->
string ->
doc:string ->
'a t ->
'b Core_kernel.Command.Param.tval make_param :
f:('a Core_kernel.Command.Arg_type.t -> 'b Core_kernel.Command.Flag.t) ->
('a, 'b) make_param