title: Add fork within an existing repo
body: <p>I have a repository on GitHub.com which contains some very useful files. These files act as a template and helper files for <code>Latex</code> code.
  I rarely change these files because they are a template, but those who use them might have to make changes to them.</p>
  
  <p>What I need is a way for those who use the files to create a <code>fork</code> into their own repository, make changes to their fork and push them, so that only their repository can see them.
  The key: a fork INSIDE another repo.</p>
  
  <p>Now, forks works not as being put into an existing repo but being beside it.
  I really need it into the existing one.</p>
  
  <p>Any clue of what I need to do?</p>
  
  <p>The very, plain, solution is downloading the files as a zip, and unzip them into a plain folder in the repository. But this way they can't be updated.</p>