[MERGE] Add a way to specify a template commit message

[John Arbash Meinel]

John Arbash Meinel has voted +1 (conditional).
Status is now: Conditionally approved
Comment:
I have to agree with Martin that it would be better to do:

msgfile = os.fdopen(tmp_fileno, 'w')
try:
finally:
   msgfile.close()

Otherwise I like it.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C20070206000121.GA28297%40jameswestby.net%3E