Enter passphrase for key, git clone, git push

git clone ssh://git@github.com/catonrug/rpi-stretch.git

Enter passphrase for key '/home/pi/.ssh/id_rsa':

To solve this in session level I can use:

ssh-add

If you receive:

Could not open a connection to your authentication agent.

This means that ssh agent is not started:

eval `ssh-agent -s`