[pred_]

> The first is that the SSH protocol provides to the server all public keys the client is willing to produce signatures for, which by default are all the public keys in your ssh-agent and in your ~/.ssh/id_*.

Not sure about other systems, but this isn't the default on Debian. I, at least, start every day by running `ssh-add ~/.ssh/id_whatever_service_I_want_to_auth_to`, because it doesn't do it by itself, and I was too lazy to configure it. For the same reason, the party trick didn't work here, since I haven't had to commit anything today yet ...