class Net::SSH::Authentication::Agent

def add_identity(priv_key, comment, lifetime: nil, confirm: false)

operation.
If confirm is true, confirmation will be required for each agent signing
seconds.
If lifetime is given, the key will automatically be removed after lifetime
Adds the private key with comment to the agent. 
def add_identity(priv_key, comment, lifetime: nil, confirm: false)
  constraints = Buffer.new
  if lifetime
    constraints.write_byte(SSH_AGENT_CONSTRAIN_LIFETIME)
    constraints.write_long(lifetime)
  end
  constraints.write_byte(SSH_AGENT_CONSTRAIN_CONFIRM) if confirm
  req_type = constraints.empty? ? SSH2_AGENT_ADD_IDENTITY : SSH2_AGENT_ADD_ID_CONSTRAINED
  type, = send_and_wait(req_type, :string, priv_key.ssh_type, :raw, blob_for_add(priv_key),
                        :string, comment, :raw, constraints)
  raise AgentError, "could not add identity to agent" if type != SSH_AGENT_SUCCESS
end