Simple way of incrementing the app versionCode when a particular task is run. Useful to increment versionCode when doing a production release build.

Android_increment_versionCode

    // Increment version code when running a production release
    def versionPropsFile = file('version.properties')
    if (versionPropsFile.canRead()) {
        def Properties versionProps = new Properties()
        versionProps.load(new FileInputStream(versionPropsFile))
        def value = 0
        def runTasks = gradle.startParameter.taskNames
        if ('assembleProductionRelease' in runTasks) {
            value = 1;
        }
        def version_Code = versionProps['VERSION_CODE'].toInteger() + value
        versionProps['VERSION_CODE'] = version_Code.toString()
        versionProps.store(versionPropsFile.newWriter(), null)
        defaultConfig {
            versionCode version_Code
        }
    } else {
        throw new GradleException("Could not read version.properties!")
    }