Utility methods for automated generation of versionName & versionCode in Android apps using semantic versioning tags

utils.gradle

/**
 * Get the version name from the latest Git tag.
 * e.g. last tag v3.0.1 -> versionName 3.0.1
 */
def computeVersionName() {
    def stdout = new ByteArrayOutputStream()
    exec {
        commandLine 'git', "--git-dir=${rootProject.rootDir}/.git", "--work-tree=${rootProject.rootDir}", 'describe', '--abbrev=0', '--tags'
        standardOutput = stdout
    }
    return stdout.toString().trim().replaceAll("v", "")
}

/**
 * Generate the version code by combining in integer format [targetSDKVersion][versionName].
 * [VersionName] follows the pattern: XYYZZ taking into account that
 * when minor/patch is only a one digit number, we complete the pattern with zeros.
 *
 * e.g. targetSdkVersion 25 and versionName 3.1.3 -> versionCode 2530103
 *
 * NOTE: the maximum versionCode allowed by Google Play is 2100000000
 */
def computeVersionCode() {
    def versionArray = computeVersionName().split("\\.")
    String major = versionArray[0]
    String minor = versionArray[1].length() < 2 ? "0" + versionArray[1] : versionArray[1]
    String patch = versionArray[2].length() < 2 ? "0" + versionArray[2] : versionArray[2]

    String versionCode = "$project.properties.target_sdk_version" + major + minor + patch
    return versionCode.toInteger()
}