PhoneGap Build already has integration with GitHub, but we host our private work repos on BeanStalk, so that does not help very much.
After some brief searching and contacting BeanStalk support, I figured out how to add my repo to PhoneGap Build.
The basic url structure is this:
Note: Make sure you url encode your password if it uses special characters, and also make sure you don't share this URL with anyone who you wouldn't want to know your password.
Note: Any PhoneGap Build collaborators will be able to see the URL with your password plainly visible.
Here are some exampes:
[username] is your username for that host
[password] is your password for that host
[reponame] is the name of your git repository
[account] is your BeanStalk account name:
More info: PhoneGap Build and BeanStalk git Repositories
Inspired by: Using Private Bitbucket Repositories With PhoneGap Build