anchor.diff:  { stdenv
   , fetchurl
  +, lib
   , which
   
   , perl
  
positive.code: , itstool
  }:
  
  stdenv.mkDerivation rec {
    name = "gtk-doc-${version}";
    version = "1.25";
  
    src = fetchurl {
      url = "mirror://gnome/sources/gtk-doc/${version}/${name}.tar.xz";
      sha256 = "1ea46ed400e6501f975acaafea31479cea8f32f911dca4dff036f59e6464fd42";
    };
  
    preConfigure =
  
negative.code:     itstool
    ];
  
    passthru = {
      srcVerification = fetchurl {
        inherit (src)
          outputHash
          outputHashAlgo
          urls;
        sha256Url = "https://download.gnome.org/sources/gtk-doc/${version}/"
          + "${name}.sha256sum";
        failEarly = true;
      };
    };
  
    meta = with lib; {
      description = "Tools for documentation embedded in GTK+/GNOME source code";
      homepage = http://www.gtk.org/gtk-doc;
      license = licenses.gpl2;
  