By the Server
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... remove public keys, and list the current
public keys known by the server. The subsystem name is "publickey".
...
... SHOULD be sent. Note that, normally, status messages are only sent
by the server (in response to requests from the client). This is the
only occasion on which the client ...
...
"command-override" specifies a command to be executed when this key
is in use. The command should be executed by the server when it
receives an "exec" or "shell" request from the client, in place of
...