有时我们用git clone克隆一个项目后，如果再使用git pull试图去更新最新代码时，会碰到如下的问题：
$ git pull
There is no tracking information for the current branch.
Please specify which branch you want to merge with.
See git-pull(1) for details
git pull <remote> <branch>
If you wish to set tracking information for this branch you can do so with:
git branch --set-upstream master origin/<branch>
解决方案： 执行git 命令： git push -u origin master
重新执行git pull,问题已解决。