[MERGE] Add tests for commit_message_template hooks.

[John Arbash Meinel]

John Arbash Meinel has voted resubmit.
Status is now: Resubmit
Comment:
This should wait until 1.8.
Otherwise I'm okay with this. Obviously it needs a NEWS entry, possibly 
an update under doc/* and there is a string that says "new in 1.7" that 
should be updated.

Also, I think we need an end-to-end commit check, that the default 
commit message is supplied at the right time. (Basically that 
generate_commit_message_template() will be called by the commit logic.)

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C20080821171306.GA24638%40vernstok.nl%3E
Project: Bazaar