build.gradle

task commitVersion {

    if (project.hasProperty("commit")) {
        print("commiting version")
        def versionPropsFile = file('version.properties')
        Properties versionProps = new Properties()
        versionProps.load(new FileInputStream(versionPropsFile))

        def versionPatchStaged = versionProps['VERSION_PATCH_STAGED'].toInteger()
        def versionBuildStaged = versionProps['VERSION_BUILD_STAGED'].toInteger()
        def versionNumberStaged = versionProps['VERSION_NUMBER_STAGED'].toInteger()

        def versionPatch = versionProps['VERSION_PATCH'].toInteger() + versionPatchStaged
        def versionBuild = versionProps['VERSION_BUILD'].toInteger() + versionBuildStaged
        def versionNumber = versionProps['VERSION_NUMBER'].toInteger() + versionNumberStaged

        versionProps['VERSION_PATCH_STAGED'] = 0.toString()
        versionProps['VERSION_BUILD_STAGED'] = 0.toString()
        versionProps['VERSION_NUMBER_STAGED'] = 0.toString()
        versionProps['VERSION_PATCH'] = versionPatch.toString()
        versionProps['VERSION_BUILD'] = versionBuild.toString()
        versionProps['VERSION_NUMBER'] = versionNumber.toString()

        versionProps.store(versionPropsFile.newWriter(), null)
    }
}

def autoincrementVersion() {
    print("Incrementing version")
    def versionPropsFile = file('version.properties')
    def runTasks = gradle.getStartParameter().getTaskRequests().toString()

    def value = 0

    if (runTasks.contains('assemble') || runTasks.contains('assembleRelease') || runTasks.contains('aR')) {
        value = 1
    }

    Properties versionProps = new Properties()
    versionProps.load(new FileInputStream(versionPropsFile))

    def versionPatch = versionProps['VERSION_PATCH_STAGED'].toInteger() + value
    def versionBuild = versionProps['VERSION_BUILD_STAGED'].toInteger() + 1
    def versionNumber = versionProps['VERSION_NUMBER_STAGED'].toInteger() + value

    versionProps['VERSION_PATCH_STAGED'] = versionPatch.toString()
    versionProps['VERSION_BUILD_STAGED'] = versionBuild.toString()
    versionProps['VERSION_NUMBER_STAGED'] = versionNumber.toString()

    versionProps.store(versionPropsFile.newWriter(), null)
}

android{
    // ... snip
    def versionPropsFile = file('version.properties')
    if (versionPropsFile.canRead()) {
        Properties versionProps = new Properties()

        versionProps.load(new FileInputStream(versionPropsFile))

        def versionMajor = versionProps['VERSION_MAJOR'].toInteger()
        def versionMinor = versionProps['VERSION_MINOR'].toInteger()
        def versionPatch = versionProps['VERSION_PATCH'].toInteger()
        def versionBuild = versionProps['VERSION_BUILD'].toInteger()
        def versionNumber = versionProps['VERSION_NUMBER'].toInteger()

        defaultConfig {
            applicationId "com.application.myapplicationhere"
            minSdkVersion 23
            targetSdkVersion 28
            versionCode versionNumber
            versionName "${versionMajor}.${versionMinor}.${versionPatch} (${versionBuild})"
        }

    } else {
        throw new GradleException("Could not read version.properties!")
    }
    
    //snip ...

}