Android build version with git commit hash

build.gradle

// merge this with your current build.gradle
// generates a version name from currently checked out git commit
def getCommitHash = { ->
    def stdout = new ByteArrayOutputStream()
    exec {
        commandLine 'git', 'rev-parse', '--short', 'HEAD'
        standardOutput = stdout
    }
    return stdout.toString().trim()
}

android {
    // ...
    defaultConfig {
        // ...
        versionName '1-' + getCommitHash()
    }
}