val oldReleasePattern = "release(\\d+)x".toRegex()
    return when (branchName) {
        "master" -> 0
        "release" -> 1
        else -> {
            val matchResult = oldReleasePattern.find(branchName)
            if (matchResult == null) {
                null
            } else {
                (matchResult.groupValues[1].toInt() - 4).apply {
                    require(this in 2..23)
                }