title: git reword without resolving merge conflicts again
body: <p>Is it possible to change commit messages using git rebase, but without having to re-resolve merge conflicts? </p>
  
  <p>I need to bowdlerize an older repo and I don't want to change any of the actual code, just the messages. </p>
  
  <p>I've tried <code>--preserve-merges</code>.</p>