▌1. Clone your fork:
git clone [email protected]:YOUR-USERNAME/YOUR-FORKED-REPO.git
▌2. Add remote from original repository in your forked repository:
cd into/cloned/fork-repo
git remote add upstream git://github.com/ORIGINAL-DEV-USERNAME/REPO-YOU-FORKED-FROM.git
git fetch upstream
▌3. Updating your fork from original repo to keep up with their changes:
git pull upstream master
参考：
https://gist.github.com/CristinaSolana/1885435
https://www.gun.io/blog/how-to-github-fork-branch-and-pull-request