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> dev
解决办法：
把本地分支跟远端分支进行关联
git branch --set-upstream-to=origin/dev dev
git branch --set-upstream-to=origin/master master
