I found this very useful in merging changes for Octopress, granted I ended up having to wipe the entire project out anyways.
git remote add upstream https://github.com/imathis/octopress.git
This way I’m able to fetch anything that happens to the master of octopress by simply running
git fetch upstream
If I want to go ahead and merge:
git merge upstream/master
I can’t tell if there’s a difference between using https:// or git://, so I’m sticking to what github uses as an example.