title: git: use "commit --cleanup=whitespace" with "rebase --interactive"
body: <p>I want to <em>always</em> use <code>--cleanup=whitespace</code> when creating/editing commit messages (to allow for initial "#"). Unfortunately, I can't find a proper setting to put in <code>~/.gitconfig</code>; this one doesn't work:</p>
  
  <pre><code>[commit]
      cleanup = whitespace
  </code></pre>
  
  <p>For normal commits I added <code>--cleanup=whitespace</code> to my main commit alias, but
  I can't figure out how to pass this option to <code>git rebase --interactive</code> so that I could reword and squash commits and use my preferred cleanup method.</p>