nixpkgs/pkgs/servers/http/nginx/default.upstream

url http://nginx.org/en/download.html
version_link '.*-([0-9]+[.][0-9]*[02468]([.][0-9]+)*)[.]tar[.][a-z0-9]*$' 

do_overwrite() {
  ensure_hash
  set_var_value version "$CURRENT_VERSION"
  set_var_value sha256 "$CURRENT_HASH"
}