Moen Tub Diverter (threaded) - copper pipe isn't

I'm just trying to give my tub a face lift. Replacing older (10 yrs) Moen, polished chrome fixtures with newer ones. Saving myself the trouble replacing shower valves. The problem is that the tub diverter that comes with the set (shower head, single handle, cover plate, etc) is a front end threaded model, and I have a non threaded copper stub.

Now what?

You can solder on a threaded adapter...trick is to cut the pipe at the proper length.