title: is this a valid git fork use-case?
body: <p>There's a github repo I'd like to fork (let's call it 'upstream') and add some tiny bits of functionality on top of it. I 'm not going to issue any pull requests for this functionality as it is too specific for my use-case. However, I want to receive updates from 'upstream', and to be able, should I stumble upon an bug, to issue a pull request.</p>
  
  <p>There's the rub though: I understand that <a href="http://blog.evan.pro/keeping-a-clean-github-fork-part-1" rel="nofollow">I should keep my fork clean</a>, meaning all work should be done in branches. I believe this is both to enable pull requests for a specific branch and to allow me to frequently update my master branch from the 'upstream'.</p>
  
  <p>How then am I going to make independent progress in my forked repository in the limited functionality I wish to add?</p>
  
  <ul>
  <li>if my functionality is added in the master branch of my forked repo then I violate the "keep the fork master branch clean" guideline</li>
  <li>if my functionality is added in a branch (for which I will never issue a pull request) then my master will never arrive at the state I want it to be (which is the 'upstream' master plus a thin layer of additional functionality that's specific to my use case as I said).</li>
  </ul>
  
  <p>What am I missing?</p>