ScriptNode.actionSignal() synchronised with the undo queue somehow?

[davidsminor]

I've currently got some tricks in a couple of the IE tools to synchronize the gaffer undo queue with maya's undo queue. I'm having to employ some tricks to work around the fact that ScriptNode.actionSignal() can get called multiple times per undoable event.

I've just written a 17 line comment explaining those tricks (badly), which is what reminded me to create this ticket! :P