diff between two revisions

[Robey Pointer]

I haven't been following all the threads closely, so I've probably  
missed something -- but I just tried to do a "diff" between two  
revisions in bzr.dev at 854, and I can't figure out how to do it.   
Neither two -r options, nor "-r 4:5", nor "-r 4-5" works.  I thought  
that got implemented a few weeks ago but now I'm not so sure.  Am I  
brain damaged? :)  How do I do this?

I'm not terrible at writing docs so maybe I can start fleshing out  
some of the help text by asking annoying questions like this.  Most  
of the commands' help texts are currently just a pile of old TODOs.

robey