anchor.diff:      mv $out/etc/zprofile $out/etc/zprofile_zwc_is_used
   
       rm $out/bin/zsh-${version}
  +    mkdir -p $out/share/doc/
  +    mv $out/share/zsh/htmldoc $out/share/doc/zsh-$version
     '';
     # XXX: patch zsh to take zwc if newer _or equal_
   
  
positive.code: stdenv.mkDerivation {
    pname = "zsh";
    inherit version;
  
    src = fetchurl {
      url = "mirror://sourceforge/zsh/zsh-${version}.tar.xz";
  
negative.code:   checkFlags = map (T: "TESTNUM=${T}") (lib.stringToCharacters "ABCDEVW");
  
    # XXX: think/discuss about this, also with respect to nixos vs nix-on-X
    postInstall = ''
      make install.info install.html
      mkdir -p $out/etc/
      cat > $out/etc/zprofile <<EOF
  if test -e /etc/NIXOS; then
  