could-not-open-a-connection-to-your-authentication-agent.

$ ssh-add
Could not open a connection to your authentication agent.

start up the ssh-agent

$ eval `ssh-agent -s`
Agent pid 17715

Try it again, it should work

$ ssh-add
Enter passphrase for /home/sotirk/.ssh/id_rsa:
Identity added: /home/sotirk/.ssh/id_rsa (/home/sotirk/.ssh/id_rsa)
$ git push -u origin master
Branch master set up to track remote branch master from origin.
Everything up-to-date