title: How to make a pull request for just a single change?
body: <p>I have almost no clue about git or github and I don't want a clue.  But I happen to have a two-line bugfix for an open source project here.  In the spirit of cooperation and whatever, I'd like to contribute it back.  If it doesn't cost me too much pain.</p>
  
  <p>So, ages ago I forked the repository, then occasionally made a few of my own modifications, and then just recently made this two-line bugfix.  Everything has been checked into the master branch and pushed back to origin.  Now I want to make a pull request for just the two-line bugfix.  It seems github doesn't provide any such facility.</p>
  
  <p>In retrospect, I probably should have made a whole separate project branch before I made my two-line bugfix, but a) that's too much administrative pain for two lines of code and b) I didn't know I'd want to be contributing the bugfix back when I wrote it.  And anyway, it's too late now.</p>
  
  <p>I could create a new branch, but that would still contain all the other garbage changes.  So it doesn't get me anywhere.  I'd like to create a new branch from upstream excluding all my local changes, then redo just this one change.  But I can't see any way to do that apart from making a whole new fork, and I don't want a whole new fork.</p>
  
  <p>Right now my best solution is to give up: the code works for me now, it's not my problem.  Anyone got a better plan?</p>