What commit did I branch off from?

Sometimes, you create a branch off another branch, do some work on it, and want to know what the original branch was pointing at. For instance, if you're looking to clean up your Git history , but don't want to rebase off origin/HEAD as you know there are some gnarly conflicts you may have to deal with, you want to know the last known "good" commit. I'd previously look down my commits, work out…