Automate Github Pull at System Startup

I will give you a Linux machine that runs in EC2, a Github repository and the corresponding SSH key. On the machine there is a PHP website running. I need the followings: 1. install git on the linux machine 2. create a cron job that at startup and once per hour pulls the sources from the git repository inside the website directory 3. a script (command) that does the git pull manually 4. some folders needs to be .gitignored