[RFC] quickbranch

[Keir Mierle]

I'm new to bzr, and sadly my introduction was not great; I branched bzrtools
and it took 4 hours. Since properly fixing the speed problem is not trivial, I
thought I'd cook up a stopgap plugin hack: make branching work at the speed of
the network. The plugin sacrifices commit speed for branch speed. The idea is
simple: at every commit, tar the branch into .bzrcache.tar.gz. This way when
someone wants to branch, they merely need to get a single tar file, avoiding
the need for rsync. The plugin also adds a quickbranch command which knows to
look for the .bzrcache.tar.gz file for fast branching.

The current code is extremely rough, but I thought I'd toss it out to see what
people think of the idea. If people think this is reasonable I'll put more time
into it (and make it work on Windows).

http://www.cs.toronto.edu/~keir/quickbranch/quickbranch.py
Instructions:
 1) Drop quickbranch.py in your .bazaar/plugins directory
 2) Add bzrlib.plugins.quickbranch.cache_branch to your post_commit hook
 3) bzr quickbranch http://url/here

Thanks in advance,
Keir