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:   ] ++ optional sslSupport  "--with-ssl"
      ++ optional saslSupport "--with-sasl";
  
    meta = {
      description = "A small but very powerful text-based mail client";
      homepage = http://www.mutt.org;
  