title: What does this disconnected arrow mean on gitk?
body: <p>What's the meaning of the blue disconnected arrow?
  Note, it happened after I added a remote head and did <code>git fetch</code>.</p>
  
  <p><img src="https://i.stack.imgur.com/pzJD9.png" alt="enter image description here"></p>
  
  <p>...</p>
  
  <p><img src="https://i.stack.imgur.com/94qJJ.png" alt="enter image description here"></p>