bug#20325: convert "fixes:debbugs:123" in log to (Bug#123) in ChangeLog

[Paul Eggert <eggert@cs.ucla.edu>]

On 04/24/2015 01:27 PM, Stefan Monnier wrote:
> I think we shouldn't look at recent commits but at all commits in
> the repository, since we want to reduce variation overall.
>

Then the counts are closer.  If one looks at the current 1,021,440-line 
output of 'git log', 3515 lines match the regular expression 
'bug#[0-9][0-9][0-9]' and 2906 lines match 'debbugs:[0-9][0-9][0-9]', 
ignoring case for both searches.

My impression is that most of the 'Fixes: debbugs:NNNNN' lines come from 
"bzr commit --fixes NNNNN", i.e., that they were not originally part of 
the commit message but were in Bzr metadata that was transferred into 
Git's commit messages because Git doesn't have metadata of this form.

I expect that most of the "by-hand" instances use the "Bug#NNNNN" form 
because it's easier to type, and now that we're doing this stuff more by 
hand the "Bug#NNNNN" form would become more popular even if CONTRIBUTE 
weren't recommending it.