anchor.diff:  
       ${cfg.config}
   
  +    ${optionalString (cfg.eventsConfig != "" || cfg.config == "") ''
  +    events {
  +      ${cfg.eventsConfig}
  +    }
  +    ''}
  +
       ${optionalString (cfg.httpConfig == "" && cfg.config == "") ''
  -    events {}
  -
       http {
         include ${cfg.package}/conf/mime.types;
         include ${cfg.package}/conf/fastcgi.conf;
  
positive.code:         ";
        };
  
        appendHttpConfig = mkOption {
          type = types.lines;
          default = "";
          description = "
            Configuration lines to be appended to the generated http block.
            This is mutually exclusive with using config and httpConfig for 
            specifying the whole http block verbatim.
          ";
        };
  
negative.code:     }''}
  
      ${optionalString (cfg.httpConfig != "") ''
      http {
        include ${cfg.package}/conf/mime.types;
        include ${cfg.package}/conf/fastcgi.conf;
  