1、执行brew update报错
fatal: bad revision ‘HEAD‘
fatal: bad revision ‘HEAD‘
fatal: Needed a single revision
You do not have the initial commit yet
fatal: Needed a single revision
cd $(brew --prefix) && git fetch && git reset --hard origin/master
2、mac中vim升级
brew install mercurial
brew install vim
原文：http://www.cnblogs.com/liubei/p/mac.html