title: Swap git submodule with own fork
body: <p>I added a submodule to my git repo like this:</p>
  
  <pre><code>$ git submodule add git://github.com/user/some-library some-library
  </code></pre>
  
  <p>I've decided I want to create a fork of that library to do some adjustments. How can i swap that submodule so that it points to my own github fork instead?</p>