anchor.diff:          c-ares = buildPackages.c-ares.override { fetchurl = stdenv.fetchurlBoot; };
           libev = buildPackages.libev.override { fetchurl = stdenv.fetchurlBoot; };
         };
  -    };
  +    });
     };
   
     fetchRepoProject = callPackage ../build-support/fetchrepoproject { };
  
positive.code:   # `fetchurl' downloads a file from the network.
    fetchurl = makeOverridable (import ../build-support/fetchurl) {
      inherit lib stdenvNoCC;
      curl = buildPackages.curl.override rec {
        # break dependency cycles
        fetchurl = stdenv.fetchurlBoot;
        zlib = buildPackages.zlib.override { fetchurl = stdenv.fetchurlBoot; };
  
negative.code:       };
        # On darwin, libkrb5 needs bootstrap_cmds which would require
        # converting many packages to fetchurl_boot to avoid evaluation cycles.
        # So turn gssSupport off there, and on Windows.
        # On other platforms, keep the previous value.
        gssSupport =
          if stdenv.isDarwin || stdenv.hostPlatform.isWindows
            then false
            else old.gssSupport or true; # `? true` is the default
        libkrb5 = buildPackages.libkrb5.override {
          fetchurl = stdenv.fetchurlBoot;
          inherit pkgconfig perl openssl;
  