title: "git pull --rebase" leads to "Cannot rebase onto multiple branches"
body: <p>So, my work environment has precisely one branch with a remote companion on Github.  I'm trying to do <code>git pull --rebase</code> in order to prevent <code>git push</code> from creating merge commit messages that don't provide new information to others working on this project and just gum up the works.  But when I try that, it gives me this:</p>
  
  <pre><code>From https://github.com/our_profile/our_repository
   * branch            HEAD        -&gt; FETCH_HEAD
  Cannot rebase onto multiple branches
  </code></pre>
  
  <p>And the pull aborts. Calling <code>git branch</code> informs me that I have only one branch on my local machine, so what's going on?</p>