An error occurred while performing `git pull` on repo `master`

pod install或者pod setup 报错如下：

[!] An error occurred while performing `git pull` on repo `master`.

[!] /usr/bin/git pull --ff-only

fatal: Not possible to fast-forward, aborting.

进入~/.cocoapods/repos/master 删除 master

重新pod setup

详情请见:https://github.com/CocoaPods/CocoaPods/issues/776

https://github.com/CocoaPods/CocoaPods/issues/948

解决问题。