anchor.diff:          type = types.lines;
           default = "";
           description = ''
  -          Extra configuration text appended to <filename>ssh_config</filename>.
  +          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.
           '';
  
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: 
          ${optionalString (cfg.pubkeyAcceptedKeyTypes != []) "PubkeyAcceptedKeyTypes ${concatStringsSep "," cfg.pubkeyAcceptedKeyTypes}"}
          ${optionalString (cfg.hostKeyAlgorithms != []) "HostKeyAlgorithms ${concatStringsSep "," cfg.hostKeyAlgorithms}"}
        '';
  
      environment.etc."ssh/ssh_known_hosts".text = knownHostsText;
  