Except for when you change from JIRA to some other project tracking tool. I think this is worth considering since project and people management trends tend to suffer from more churn than version control systems.

In my book, it's easier to auto-import sensible git logs into JIRA than trying to do the reverse. Then again, I'm of the opinion that git history matters, specifically for commit messages. Otherwise, you might as well create a pre-commit hook pointing to http://whatthecommit.com