Tim Pope's article on commit messages is the gold standard. http://tbaggery.com/2008/04/19/a-note-about-git-commit-messa...
Why is better to write in that form?
See: http://stackoverflow.com/questions/3580013/should-i-use-past...
Also the past repeats: http://news.ycombinator.com/item?id=2079612
For a good laugh: http://whatthecommit.com/
It makes more sense to me that the trouble ticket ticket should be written in the imperative and the commit message should be past tense.