Auto increment version code and version name. This gist borrows heavily the code from https://gist.github.com/luciofm/923a9f35f2175dda7ad7.

build.gradle

//module gradle
apply from: 'versionCode.gradle' //anywhere


android {
    defaultConfig {
        versionName VERSION_NAME
        versionCode Integer.parseInt(VERSION_CODE)
    }
}

gradle.properties

//module directory
VERSION_NAME=1.0.1
VERSION_CODE=1

versionCode.gradle

//module directory
task('increaseVersionCode') << {
    def versionCode = Integer.parseInt(VERSION_CODE) + 1
    def versionName = VERSION_NAME.split("\\.")
    def last = Integer.parseInt(versionName[versionName.length - 1])
    versionName[versionName.length - 1] = Integer.toString(last + 1)
    versionName = versionName.join(".")

    ant.propertyfile(file: "gradle.properties") {
        entry(key: "VERSION_CODE", value: versionCode)
        entry(key: "VERSION_NAME", value: versionName)
    }
}

tasks.whenTaskAdded { task ->
    if (task.name == 'generateReleaseBuildConfig') {
        task.dependsOn('increaseVersionCode')
    }
}