anchor.diff:  
     src = fetchurl {
       url = "http://notmuchmail.org/releases/${name}.tar.gz";
  -    sha256 = "1fyx20rjpwbf2j1v5fpa5s0rjnwhcgvijzh2qyinp8rlbh1qxmab";
  +    sha256 = "1pvn1n7giv8n3xlazi3wpscdqhd2yak0fgv68aj23myr5bnr9s6k";
     };
   
     nativeBuildInputs = [ pkgconfig ];
  
positive.code: with stdenv.lib;
  
  stdenv.mkDerivation rec {
    version = "0.25.3";
    name = "notmuch-${version}";
  
    passthru = {
  
negative.code:         "{}" ";"
  
      for src in \
        util/crypto.c \
        notmuch-config.c \
        emacs/notmuch-crypto.el
      do
  