Ability to reject commit without an issue key but only for selected branches

Hi,

We recently went from Jira OnDemand SVN to Git on BitBucket.

One thing we miss alot, is the ability to demand users entering a Jira issue key, when checking in code.

I know that Git is distributed, and a lot of the checkin/commit stuff is handled locally.
But if i Jira issue check was done by BitBucket, no code could be added to "final destination" without an Jira issue key defined in the commit description.

So this feature request is, that you possibly come up with a clever idea for this :o)

Best regards
Peter Meyer