Install and configure Git on debian-based systems.

setup_git.sh

sudo aptitude -y install git
sudo su - jenkins
git config --global user.name "Jenkins CI"
git config --global user.email "[email protected]"
ssh-keygen -t rsa -C "[email protected]" # Use all the default options, don't specify
                                          # a password.
cat .ssh/id_rsa.pub # Grant this SSH key access to your Git repositories.

# If you're using github, you'll also want to do:
ssh [email protected]
# And accept the connection so that you add github.com to your known_hosts file.