来源：
https://github.com/bobthecow/git-flow-completion/wiki/Install-Bash-git-completion

我这里安装时通过HomeBrew安装：

Homebrew

1. Install homebrew

2. Install Git and bash-completion:

   brew install git && brew install bash-completion

   (Note: If this install fails with a 404 error, and you already have git installed, just remove the git part of this brew install)

3. Add bash-completion to your

   ~/.bash_profile:

   if [ -f $(brew --prefix)/etc/bash_completion ]; then
     . $(brew --prefix)/etc/bash_completion
   fi