don't use "fix xyz" in git commit messages

[Graham Percival]

For more visibility: saying "fix 123" only means something to
people who have memorized all 600+ open bugs.

- please give a short description of the actual code change, like
  "foo grob now avoids collisions with baz (123)".
  I think it's still useful to add the issue number, but that
  should only come after an English summary of the change.
  (and I suggest we use parentheses to indicate that the number
  is an issue number)

- if your patch includes a syntax change, please add "(syntax)" to
  the short git commit


We have about 20 patches coming in each week, with a backlog of
about 50 patches.  Unless we start driving developers away, we
need to be able to scan+review lots of patches regularly, and
better commit messages will help a lot.

Cheers,
- Graham