title: How to delete a git working tree branch when its working directory has been removed?
body: <p>I've removed its working directory, because this git working tree is no longer useful, then I <code>git branch -D pubsub-sketch-tree</code> at the directory of main repository. An error thrown:</p>
  
  <pre><code>error: Cannot delete branch 'pubsub-sketch-tree' checked out at '/Users/zhouhancheng/编程/github_own/sketch_worktree/pubsub-sketch_tree'  
  </code></pre>
  
  <p>But '/Users/zhouhancheng/编程/github_own/sketch_worktree/pubsub-sketch_tree' had been removed. </p>