title: Remove tracking branches no longer on remote
body: <p>Is there a simple way to delete all tracking branches whose remote equivalent no longer exists?</p>
  
  <p>Example:</p>
  
  <p>Branches (local and remote)</p>
  
  <ul>
  <li>master</li>
  <li>origin/master</li>
  <li>origin/bug-fix-a</li>
  <li>origin/bug-fix-b</li>
  <li>origin/bug-fix-c</li>
  </ul>
  
  <p>Locally, I only have a master branch. Now I need to work on <em>bug-fix-a</em>, so I check it out, work on it, and push changes to the remote. Next I do the same with <em>bug-fix-b</em>.</p>
  
  <p>Branches (local and remote)</p>
  
  <ul>
  <li>master</li>
  <li>bug-fix-a</li>
  <li>bug-fix-b</li>
  <li>origin/master</li>
  <li>origin/bug-fix-a</li>
  <li>origin/bug-fix-b</li>
  <li>origin/bug-fix-c</li>
  </ul>
  
  <p>Now I have local branches <em>master</em>, <em>bug-fix-a</em>, <em>bug-fix-b</em>. The Master branch maintainer will merge my changes into <em>master</em> and delete all branches he has already merged.</p>
  
  <p>So the current state is now:</p>
  
  <p>Branches (local and remote)</p>
  
  <ul>
  <li>master</li>
  <li>bug-fix-a</li>
  <li>bug-fix-b</li>
  <li>origin/master</li>
  <li>origin/bug-fix-c</li>
  </ul>
  
  <p>Now I would like to call some command to delete branches (in this case <em>bug-fix-a</em>, <em>bug-fix-b</em>), which are no longer represented in the remote repository.</p>
  
  <p>It would be something like the existing command <code>git remote prune origin</code>, but more like <code>git local prune origin</code>.</p>