title: Unable to find current origin/master revision in submodule path
body: <p>In my project (which uses <code>git</code>), I need to use <a href="https://github.com/mb21/JSONedit" rel="noreferrer">a library</a>, which is still in progress. I decided to create a submodule for that library, because I want to update from time to time its latest version (I don't plan to make my own change there).</p>
  
  <p>I did:</p>
  
  <pre><code>git submodule add https://github.com/mb21/JSONedit.git
  git commit -am 'added JSNedit submodule'
  git push -u origin master
  git pull origin master
  </code></pre>
  
  <p>Then, I did see the JSONedit folder in my local folder, and a link in my git folder online. But when I did <code>git submodule update --remote JSONedit/</code>, I got the following errors: </p>
  
  <pre><code>fatal: Needed a single revision
  Unable to find current origin/master revision in submodule path 'JSONedit'
  </code></pre>
  
  <p>Does anyone know what's wrong here?</p>