克隆fork仓库到本地
git clone git@github.com:YOUR-USERNAME/YOUR-FORKED-REPO.git
添加源仓库的远程主机
cd fork-repo
git remote add upstream git://github.com/ORIGINAL-DEV-USERNAME/REPO-YOU-FORKED-FROM.git
git fetch upstream
从源仓库pull更新本地仓库
git pull upstream master
推送更新到远程的fork仓库
git push