Well, the 'diffing dir...' output is incomplete; that's not the part that takes
long.  I've been meaning to submit a patch so that it adds a new output
(something like 'resolving conflicts').  That's the slow part.

I think the only real progress will be when we switch to the new way of handling
conflicts, which might not be for a while.

We're working on it! (or rather, David and Jason are!)