copy a secret key from GnuPG's gpg-agent to OpenSSH's ssh-agent

 agent-transfer is a simple utility to extract a secret RSA or Ed25519
 key from GnuPG's gpg-agent and send it to a running ssh-agent. This
 is useful for those who prefer the runtime semantics and behavior of
 OpenSSH's ssh-agent, but whose secret keys are held in long-term
 storage by GnuPG's gpg-agent.
 .
 This tool comes from the monkeysphere project.