anchor.diff:      ++ optional headerCache  gdbm
       ++ optional sslSupport   openssl
       ++ optional saslSupport  cyrus_sasl
  -    ++ optional gpgmeSupport gpgme
  -    ++ optional withSidebar  autoreconfHook;
  +    ++ optional gpgmeSupport gpgme;
   
     configureFlags = [
       (enableFeature headerCache  "hcache")
  
positive.code: { stdenv, fetchurl, fetchpatch, ncurses, which, perl, autoreconfHook
  , gdbm ? null
  , openssl ? null
  , cyrus_sasl ? null
  , gpgme ? null
  , aclocal ? null
  , headerCache  ? true
  , sslSupport   ? true
  , saslSupport  ? true
  , gpgmeSupport ? true
  , imapSupport  ? true
  , withSidebar  ? false
  , withTrash    ? false
  }:
  
  assert headerCache  -> gdbm       != null;
  
negative.code: 
  stdenv.mkDerivation rec {
    name = "mutt-${version}";
    version = "1.7.0";
  
    src = fetchurl {
      url = "http://ftp.mutt.org/pub/mutt/${name}.tar.gz";
      sha256 = "0idkamdiwj9fgqaz1vzkfg78cnmkzp74skv0ibw2xjfq6ds9hghx";
    };
  
    buildInputs =
  