https://help.github.com/articles/caching-your-github-password-in-git/#platform-all
If you're cloning repositories using HTTPS, you can use a credential helper to tell Git to remember your username and password every time it talks to the server.
If you clone repositories using SSH, then you authenticate using SSH keys instead of a username and password. For help setting up an SSH connection, see Generating SSH Keys.
Tip: You need Git 1.7.10 or newer to use the credential helper.