假设原仓库为 https://github.com/lmshao/OldHub.git，
fork后的新仓库为：[email protected]:lmshao/NewHub.git。
1. clone新仓库
$git clone [email protected]:lmshao/NewHub.git
Cloning into 'NewHub'...
Resolving deltas: 100% (1/1), done.
remote: Total 7 (delta 1), reused 0 (delta 0), pack-reused 0
$cd NewHub/ # 进入工程目录
2. 添加原仓库的远程链接
设置原仓库的别名为OldHub，默认的别名为origin。
$git remote add OldHub https://github.com/lmshao/OldHub.git
查看远程仓库信息
$git remote -v
OldHub https://github.com/lmshao/OldHub.git (fetch)
OldHub https://github.com/lmshao/OldHub.git (push)
origin [email protected]:lmshao/NewHub.git (fetch)
origin [email protected]:lmshao/NewHub.git (push)
OldHub为原仓库的别名，origin指新仓库
3. 获取远程仓库内容
$git fetch OldHub #其实获取的是仓库信息
warning: no common commits
* [new branch] master -> OldHub/master
查看所有分支
$git branch -a
* master
remotes/OldHub/master #原仓库远程分支
remotes/origin/HEAD -> origin/master
remotes/origin/master
4. Merge远程仓库分支的内容到新分支
merge的时候可以把远程分支下下来进行merge，也可以直接merge远程的分支。
方法一：下载远程仓库进行merge
$git checkout -b OldMaster remotes/OldHub/master # 新建并切换到OldMaster分支，从远程分支下载内容到此分支
Branch 'OldMaster' set up to track remote branch 'master' from 'OldHub'.
Switched to a new branch 'OldMaster'
$git branch #查看本地分支
* OldMaster
master
$git checkout master # 切换到新仓库的master分支
Switched to branch 'master'
Your branch is up to date with 'origin/master'.
$git merge OldMaster # merge原仓库的master分支
fatal: refusing to merge unrelated histories
$git merge OldMaster --allow-unrelated-histories # merge出错的话使用此命令
Auto-merging README.md
CONFLICT (add/add): Merge conflict in README.md
Automatic merge failed; fix conflicts and then commit the result.
方法二：不下载远程仓库，merge远程分支
$git merge OldHub/master # merge原仓库的master分支
$git merge OldHub/master --allow-unrelated-histories # merge出错的话使用此命令
Auto-merging README.md
CONFLICT (add/add): Merge conflict in README.md
Automatic merge failed; fix conflicts and then commit the result.
5. 推送到远程分支
$git push
or
$git push -u origin master