title: Change old commit message using `git rebase`
body: <p>I was trying to edit an old commit message as explained <a href="http://schacon.github.io/history.html" rel="noreferrer">here</a>.</p>
  <p>The thing is that now, when I try to run <code>rebase -i HEAD~5</code> it says <code>interactive rebase already started</code>.</p>
  <p>So then I try: <code>git rebase --continue</code> but got this error:</p>
  <pre><code>error: Ref refs/heads/master is at 7c1645b447a8ea86ee143dd08400710c419b945b but expected c7577b53d05c91026b9906b6d29c1cf44117d6ba
  fatal: Cannot lock the ref 'refs/heads/master'.
  </code></pre>
  <p>Any ideas?</p>