title: git add remote tracking branch to bare repo
body: <ol>
  <li>I have a bare repo that was cloned from git.drupal.org.</li>
  <li>I have cloned from this bare repo to various different websites. </li>
  <li>From each of these, I push a site-specific branch onto the bare repo.</li>
  </ol>
  
  <p>E.g. if I have foo.org and bar.org, then my bare repo has drupal's branches + one called foo and one called bar.</p>
  
  <p>The idea was that I could make the most of git's hard links to save disk space with local clones. I thought I would keep the bare repo fetching from git.drupal.org, and pull changes down to my local copies, foo &amp; bar. Then when an update came along it would be easy.</p>
  
  <pre><code>bare-repo$ git fetch &gt;/dev/null ; git branch -a
  * 7.x
    foo
    bar
    remotes/origin/7.x
    remotes/origin/8.x
  </code></pre>
  
  <p>foo and bar started out on branch 7.x but I'd like to update them to 7.8, e.g. by <code>git rebase 7.8</code> but this fails:</p>
  
  <pre><code>fatal: Needed a single revision
  invalid upstream 7.8
  </code></pre>
  
  <p>foo and bar cannot 'see' the bare repo's remotes. What can I do?</p>