title: Make Git repo public without revealing past commits
body: <p>I have a private repo that had a bunch of sensitive data committed.  However, I recently cleaned up all of the sensitive data so that it can be public.  If I change a private repo on GitHub to become public, are all past commits visible (i.e. could someone see that sensitive data from the past)?</p>
  
  <p>If so, how do I make the repo public without making the past commit history public?</p>