(defn session
  "Start a SSH session.
Requires hostname.  you can also pass values for :username, :password and :port
keys.  All other option key pairs will be passed as SSH config options."
  [agent? & options]
  (let [agent-provided? (ssh-agent? agent?)
        agent (if agent-provided? agent? *ssh-agent*)
        hostname (if agent-provided? (first options) agent?)
        options (if agent-provided? (rest options) options)
        options (apply hash-map options)]
    (session-impl agent hostname
                  (or (options :username) (. System getProperty "user.name"))
                  (options :port)
                  (options :password)
                  (dissoc options :username :port :password))))