# check your remotes
git remote -v
# origin git@github.com:YOUR_USERNAME/YOUR_FORK.git (fetch)
# origin git@github.com:YOUR_USERNAME/YOUR_FORK.git (push)
# add the remote
git remote add upstream git@github.com:ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git
# note, the original docs assume you don't have a github account set up properly. If not, do this one:
# git remote add upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git
# and confirm
git remote -v
# might look like this:
# origin https://github.com/YOUR_USERNAME/YOUR_FORK.git (fetch)
# origin https://github.com/YOUR_USERNAME/YOUR_FORK.git (push)
# upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git (fetch)
# upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git (push)
# get the changes from the originating repo
git fetch upstream
# check out the master branch to sync to
git checkout master
# and sync away
git merge upstream/master
# then back to your branch and continue
git co this-is-my-branch
git rebase master
git push --force origin this-is-my-branch
# etc.