Pass trigger function to untrigger function

What is the enhancement in mind? How should it look and feel?

Right now if you have a custom condition you have to pass a trigger and untrigger function.  Usually the untrigger is just the inverse of the trigger.

It would be nice to not have to make changes to both functions (without breaking compatibility of course).

One way to do this is to pass the trigger function to untrigger; if you don't want to do anything special you could just make your untrigger function do this:

  function(trigger)
    return not trigger()
  end

(this is for a status trigger; event trigger would need the event too).

You could even make this the default untrigger, if untrigger is blank.