anchor.diff:    # A function that builds a "native" stdenv (one that uses tools in
     # /usr etc.).  
     makeStdenv =
  -    {gcc, fetchurl, extraPath ? []}:
  +    { gcc, fetchurl, extraPath ? [], overrides ? (pkgs: { }) }:
   
       import ../generic {
         name = "stdenv-native";
  
positive.code:   };
  
  
    # Using that, build a stdenv that adds the `replace' command (which
    # most systems don't have, so we mustn't rely on the native
    # environment providing it).
    stdenvBoot2 = makeStdenv {
      inherit gcc fetchurl;
      extraPath = [stdenvBoot1Pkgs.replace];
    };
  
  
  
negative.code: 
        fetchurlBoot = fetchurl;
  
        inherit system shell gcc overrides;
      };
  
  
  