[MERGE] Add tests for commit_message_template hooks.

[John Arbash Meinel]

John Arbash Meinel has voted tweak.
Status is now: Conditionally approved
Comment:
I think it would be reasonable as a blackbox smoke test. With 'run_bzr' 
you can modify the current list, "run" a command, and then reset the 
list.

I would have otherwise suggested a whitebox test, but you can't because 
all this code is in the cmd_commit.run().

I have the feeling it would be better to have a richer api for 
commit(message_callback=XXX). Right now it only takes the Commit object, 
but it could (in theory) take a default commit message. However, this is 
a reasonable improvement.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C1220673904.25141.15.camel%40ganieda.vernstok.nl%3E
Project: Bazaar