public function getUpgrade(int $type = self::GROUP_PATCH) : string
{
$value = \Airship\expand_version($this->currentVersion);
$value += $type;
$value -= $value % $type;
return \implode('.', [self::getGroup($value, self::GROUP_MAJOR), self::getGroup($value, self::GROUP_MINOR), self::getGroup($value, self::GROUP_PATCH)]);
}