Ubuntu 16.04 comes with Git 2.7.x, which is a little old now. As versions 2.8 & 2.9 are not part of the Ubuntu repositories, you need to add the git-core personal package archive.
Open up a terminal and run the following commands, supplying your password when prompted.
sudo add-apt-repository ppa:git-core/ppa sudo apt-get update sudo apt-get install git
如果在执行第一条命令的时候出现：
sudo: add-apt-repository: command not found
可以先执行以下命令：
sudo apt-get install software-properties-common python-software-properties