I created keys as instructed in the github tutorial, registered them with github, and tried using ssh-agent explicitly — yet git continues to ask me for my passphrase every time I try to do a pull or a push.
What could be the cause?
Once you have started the SSH agent with:
you have to add your private key to it:
This will ask you your passphrase just once, and then you should be allowed to push, provided that you uploaded the public key to Github.