Get version from git tagging

git-help.gradle

// Copy and paste the content of this file in app/build.gradle
//  Now you are able to use it under defaultConfig, for example:  
//    versionCode getRevCount()
//    versionName getTag() + '-' + getRevHash()

System.println( "App: " + "com.example.app" + " v" + getTag() + '-' + getRevHash() + "(" + getRevCount() + ")" )

def getTag() {
    def cmd1 = "git rev-list --tags --max-count=1"
    def proc1 = cmd1.execute()
    def cmd2 = "git describe --tags " + proc1.text.trim()
    def proc2 = cmd2.execute()
    def revision = proc2.text.trim()
    return revision
}

def getRevCount() {
    def cmd = "git rev-list --all --count"
    def proc = cmd.execute()
    def revision = Integer.valueOf(proc.text.trim())
    return Integer.valueOf(revision)
}

def getRevHash() {
    def cmd = "git rev-parse --short HEAD"
    def proc = cmd.execute()
    def revision = proc.text.trim()
    return revision
}