From:
http://stackoverflow.com/questions/1123344/merging-between-forks-in-github
1. 添加remote original 分支，名字貌似喜欢叫upstream
git remote add upstream git://github.com/octocat/Spoon-Knife.git
2. fetch
git fetch upstream
3. 然后会看到各种versions
From git://github.com/octocat/Spoon-Knife.git * [new branch] gh-pages -> upstream/gh-pages * [new branch] master -> upstream/master
4. Merge 或者 pull
git merge upstream/master
或者pull
git pull upstream/master
原文：http://www.cnblogs.com/liangnote/p/5006710.html