Notes about how I used this.
- Needed run ssh-keygen as www-data user to create the .ssh keys used by github.
- Created a var/www/.ssh folder to place ssh key in, as well as allow Recognized hosts file creation.
- Manually used git clone as user www-data to pull master branch down, and answered any prompts.
Once I did things as user www-data instead of ubuntu doing a git deploy worked like a charm.
Thanks to these two links..
http://jondavidjohn.com/git-pull-from-a-php-script-not-so-simple/