anchor.diff:  
           ${optionalString (cfg.pubkeyAcceptedKeyTypes != []) "PubkeyAcceptedKeyTypes ${concatStringsSep "," cfg.pubkeyAcceptedKeyTypes}"}
           ${optionalString (cfg.hostKeyAlgorithms != []) "HostKeyAlgorithms ${concatStringsSep "," cfg.hostKeyAlgorithms}"}
  -
  -        ${cfg.extraConfig}
         '';
   
       environment.etc."ssh/ssh_known_hosts".text = knownHostsText;
  
positive.code:     # generation in the sshd service.
      environment.etc."ssh/ssh_config".text =
        ''
          AddressFamily ${if config.networking.enableIPv6 then "any" else "inet"}
  
          ${optionalString cfg.setXAuthLocation ''
  
negative.code:         type = types.lines;
          default = "";
          description = ''
            Extra configuration text prepended to <filename>ssh_config</filename>. Other generated
            options will be added after a <code>Host *</code> pattern.
            See <citerefentry><refentrytitle>ssh_config</refentrytitle><manvolnum>5</manvolnum></citerefentry>
            for help.
          '';
  