anchor.diff:  
     # Install mug and msg2pdf
     postInstall = stdenv.lib.optionalString withMug ''
  -    cp -v toys/msg2pdf/msg2pdf $out/bin/
  -    cp -v toys/mug/mug $out/bin/
  +    for f in msg2pdf mug ; do
  +      install -m755 toys/$f/$f $out/bin/$f
  +    done
     '';
   
     meta = with stdenv.lib; {
  
positive.code: 
    # pmccabe should be a checkInput instead, but configure looks for it
    buildInputs = [
      sqlite xapian glib gmime texinfo emacs guile libsoup icu pmccabe
    ] ++ stdenv.lib.optionals withMug [ gtk3 webkitgtk24x ];
    nativeBuildInputs = [ pkgconfig autoreconfHook ];
  
    doCheck = true;
  
  
negative.code: { stdenv, fetchFromGitHub, sqlite, pkgconfig, autoreconfHook, pmccabe
  , xapian, glib, gmime, texinfo , emacs, guile
  , gtk3, webkitgtk24x, libsoup, icu
  , withMug ? false }:
  
  stdenv.mkDerivation rec {
    name = "mu-${version}";
    version = "0.9.18";
  
    src = fetchFromGitHub {
      owner  = "djcb";
      repo   = "mu";
      rev    = version;
      sha256 = "0zy0p196bfrfzsq8f58xv04rpnr948sdvljflgzvi6js0vz4009y";
    };
  
    # as of 0.9.18 2 tests are failing but previously we had no tests
  