I imagine this is done a lot with no problem, but I was just a little nervous about adding the raw garlic without letting it pickle in the brine first; after it’s covered with oil it could be anaerobic, which, if the pH is not low enough could create conditions for botulism. That’s a stretch, I know, and if the garlic were in the brine it wouldn’t happen, so there’s probably nothing to worry about. Still … I’m interested in what others have to say.