anchor.diff:  
     mainCfg = config.services.httpd;
   
  -  httpd = pkgs.apacheHttpd.override { mpm = mainCfg.multiProcessingModule; };
  +  httpd = mainCfg.apacheHttpd;
  +
  +  httpdConf = mainCfg.configFile;
   
     php = pkgs.php.override { apacheHttpd = httpd; };
   
  
positive.code:   '';
  
  
    httpdConf = pkgs.writeText "httpd.conf" ''
  
      ServerRoot ${httpd}
  
  
negative.code:         ";
        };
  
        apacheHttpd = mkOption {
          default = pkgs.apacheHttpd.override { mpm = mainCfg.multiProcessingModule; };
  	example = "pkgs.apacheHttpd_2_4";
          description = "
            Overridable attribute of the Apache HTTP Server package to use.
          ";
        };
  
        configFile = mkOption {
          default = confFile;
  	example = ''pkgs.writeText "httpd.conf" "# my custom config file ...";'';
          description = "
            Overridable config file to use for Apache. By default, use the
            file automatically generated by nixos.
          ";
        };
  
        extraConfig = mkOption {
          default = "";
          description = "
            These configuration lines will be appended to the Apache config
            file. Note that this mechanism may not work when <option>configFile</option>
            is overridden.
          ";
        };
  
  