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

[Paul Eggert]

Dmitry Gutov wrote:
> We've used the debbugs:1234 format in commit messages for a while now.

We've used several formats.  "Fixes: debbugs:NNNN" is designed for Bzr I think, 
"(Bug#NNNN)" is the more-traditional form, and CONTRIBUTE currently recommends a 
third format "Fixes: bug#NNNN".

In practice, about as many commits these days use the Bzr-ish format as use the 
more-traditional form (see (*) below).  I don't know why we're still using a 
Bzr-ish format (is it just inertia?), and I don't know why CONTRIBUTE disagrees 
with both the commonly-used formats.

Since we're not using Bzr any more, how about if we change CONTRIBUTE to suggest 
the more-traditional "(Bug#NNNN)" form?  Any new technology that replaces 
debbugs would have to handle the same bug numbers as before, I expect.

(*) I surveyed the 2213 commits since November 1 (this is a bit before the Git 
transition), i.e., all commits from d87931d249a4c7f15d4c1178c6ce396ab18ce1f6 
through 35be45bbc9ac525bb2bc3e20b0fa27c1ceee0c15, and found the following number 
of instances of each format:

 count  example of the style
 262    Fixes: debbugs:20357
 172    (Bug#20011)
  49    (bug#20276)
  24    Fixes: bug#20338
   8    Fix bug#19891
   6    Fixes: Bug#20338
   5    Fixes: 18757
   5    Fixes Bug#15880.
   2    Fixes: debbugs:19387 debbugs:19405
   1    Fixes: debbugs:19134.
   1    Fixes: big#19528
   1    Fixes (bug#17284).
   1    Fix Bug#20249