有时候新创建的分支执行
git pull
会出现：

$ 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-to=origin/<branch> b

直接执行：
git branch --set-upstream-to=origin/远程分支的名字

例子：

假如当前在本地分支c

要和远程分支a建立跟踪信息；
执行：
git branch --set-upstream-to=origin/a