nixpkgs/pkgs/development/libraries/botan/unstable.upstream

url http://botan.randombit.net/download.html
version_link 'Botan-[0-9]+[.][0-9]+([.][0-9]+)?[.](tgz|tbz|tbz2|tar[.]bz2)$'
ensure_version
attribute_name botanUnstable
do_overwrite(){
  ensure_hash
  set_var_value sha256 $CURRENT_HASH
  set_var_value baseVersion ${CURRENT_VERSION%.*}
  set_var_value revision ${CURRENT_VERSION##*.}
}