This gem provides a command line utility called 'hush' which can manage secret info. This was built to solve my problem of not wanting to store email addresses and other sensitive info in my github managed dotfiles project.
The hushs are not meant to be cryptographically secure. They are stored in a yaml file (~/.hush.yml) and are protected by unix file permissions. This is similar to how ssh private keys are stored in an ~/.ssh directory.
git config user.email ${hush my_email}
This will store the value of my_email in your git config. If my_email is not known to hush, you will be prompted to supply it and it will be remembered from then on.