ubuntu升级已安装git版本

# To get the very latest version of git, you need to add the PPA (Personal Package Archive) from the Ubuntu Git Maintainers Team to your Software Source list. Do that with the add-apt-repository command to add the PPA:

sudo add-apt-repository ppa:git-core/ppa

# Then update the source list and upgrade git:
sudo apt-get update
sudo apt-get install git