Updating a fork

gistfile1.txt

Reference: http://stackoverflow.com/questions/7244321/how-to-update-github-forked-repository

First time: Add the remote, call it "upstream", for example:

   git remote add upstream https://github.com/whoever/whatever.git

Fetch all the branches of that remote into remote-tracking branches,
such as upstream/master:

   git fetch upstream

Make sure that you're on your master branch:

   git checkout master

Rewrite your master branch so that any commits of yours that
aren't already in upstream/master are replayed on top of that
other branch:
   git rebase upstream/master
   
If you don't want to rewrite the history of your master branch, 
(for example because other people may have cloned it) then you should 
replace the last command with git merge upstream/master. However, for 
making further pull requests that are as clean as possible, it's probably 
better to rebase.

Update: If you've rebased your branch onto upstream/master you may need 
to force the push in order to push it to your own forked repository on GitHub. 
You'd do that with:

   git push -f origin master