Download :
curl https://raw.githubusercontent.com/git/git/master/contrib/completion/git-completion.bash -o ~/.git-completion.bash
Add this code to .bash_profile
if [ -f ~/.git-completion.bash ]; then
. ~/.git-completion.bash
fi
Make it executable :
chmod +x ~/.git-completion.bash
Reload the profile
. ~/.bash_profile
Credits : thanks to Matt Cone