Private key export for SSH

[John Lane]

This is just an observation. I thought that perhaps, if I had an
extracted private key, that I could use "ssh-add" to add it and remove
the need to manually edit "sshcontrol". I tried:

$ ssh-add alice.key
Identity added: alice.key (alice.key)

Looking good. However...

$ ssh-add -l
The agent has no identities.

No joy. I realise the documented way is to edit the sshcontrol file and
put the keygrip into it. But the positive output above is misleading.

That's where gpg knows about the key (e.g. on the machine where the
extract was done). The "ssh-add alice.key" works if the key is unknown
to gpg - the keygrip is written to sshcontrol and to private-keys-v1.d.
furthermore, importing the alice.gpg key afterwards works fine too.

# RSA key added on: 2016-10-12 15:44:05
# MD5 Fingerprint:  d0:d1:43:af:ec:4a:4c:92:7c:af:1f:70:92:13:89:16
817A3B5A8596096E8AC2932617C10E4181F09B55 0