Bisect plugin updated

[Jeff Licquia]

James Westby wrote:
> Yeah, I think that is pretty much what needs to happen. It obviously
> needs to pass review, and I think Jeff will have to sign a copyright
> assignment if he hasn't already.

I can assign copyright, if someone can point me to the official procedure.

Hints for review: in particular, it might be good to verify that my 
handling of the working tree is correct.  To travel forward/back in 
time, I basically do the equivalent of "bzr revert -r [rev]".

It's also worth noting that my familiarity with the bzr API is so low, 
that I could be doing any number of other stupid things in there.  But 
it does pass my tests, and has been used in real life by me at least.