[MERGE][Take two] Show the diff in the commit messages

[Aaron Bentley]

Aaron Bentley has voted -1.
Status is now: Vetoed
Comment:
Detecting metadata lines based on their prefix is not tasteful, and is 
also not reliable.  For example, removing a file line whose contents are 
"--\xa0" will produce a diff line "---\x0" which does not indicate a 
file path and is not utf-8-encoded.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C200707162039.10687.kreijack%40tiscalinet.it%3E