Subversion plugin - cannot diff two branches

I'm new to IDEA. I'm testing the usage of the subversion plugin and have ran into an issue. I cannot diff two source branches using the IDEA.

Is this plugin under active development? The svnup.tigris.org page shows no activity on the devlist. Am I looking in the right area? I would think that this is a key feature....

THanks!
Ruel Loehr