Refer: https://askubuntu.com/questions/579589/upgrade-git-version-on-ubuntu-14-04
$ sudo add-apt-repository ppa:git-core/ppa
$ sudo apt-get update
$ sudo apt-get install git
$ git --version

Technical notes, and other ideas.
Refer: https://askubuntu.com/questions/579589/upgrade-git-version-on-ubuntu-14-04
$ sudo add-apt-repository ppa:git-core/ppa
$ sudo apt-get update
$ sudo apt-get install git
$ git --version