anchor.diff:  
     httpd = pkgs.apacheHttpd;
   
  +  inherit (pkgs.lib) addDefaultOptionValues optional concatMap concatMapStrings;
  +  
   
     makeServerInfo = cfg: {
       # Canonical name must not include a trailing slash.
  
positive.code: 
    callSubservices = serverInfo: defs:
      let f = svc:
        let config = pkgs.lib.addDefaultOptionValues res.options svc.config;
            res = svc.function {inherit config pkgs serverInfo;};
        in res;
      in map f defs;
  
negative.code:         makeVirtualHost = vhostIn:
            let
              # Fill in defaults for missing options.
              vhost = addDefaultOptionValues perServerOptions vhostIn;
            in ''
              <VirtualHost *:*>
                  ${perServerConf false vhost}
  