title: Can I add metadata to git commits? Or can I hide some tags in gitk
body: <p>I want to associate custom metadata with a <code>git commit</code>.  Specifically to record a review ID from a code review but it could be anything.  Tags seem a natural way to do that but I expect to have a review for every commit and I don't want to clutter <code>gitk</code> with tons of tags.  Is there some other mechanism to add custom metadata?  Can I make certain tags invisible?  If I could tell <code>gitk</code> not to display tags matching some pattern or RE, that would likely work but I don't see a way to do that.</p>