step1 下载

https://github.com/git/git/blob/master/contrib/completion/git-completion.bash

step2 加载到环境变量

source git-completion.bash

step3 添加到shell启动文件可以实现自动加载环境变量

# 1
mv git-completion.bash /etc/profile.d/
# 2
vim ~/.bashrc
# edit