Android Gradle sign and increment version for release

build.gradle

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.6.+'
    }
}

apply plugin: 'android'

repositories {
    mavenCentral()
}

dependencies {
  //list your dependencies 
}

android {
    compileSdkVersion 19
    buildToolsVersion "19"

    defaultConfig {
        //only needed for release, see release Task
        versionCode 0
        versionName ""
        minSdkVersion 10
        targetSdkVersion 19
    }

    sourceSets {
        main {
            //or whatever your structure is
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src']
            resources.srcDirs = ['src']
            aidl.srcDirs = ['src']
            renderscript.srcDirs = ['src']
            res.srcDirs = ['res']
            assets.srcDirs = ['assets']
        }

        // Move the tests to tests/java, tests/res, etc...
        instrumentTest.setRoot('tests')

        // Move the build types to build-types/<type>
        // For instance, build-types/debug/java, build-types/debug/AndroidManifest.xml, ...
        // This moves them out of them default location under src/<type>/... which would
        // conflict with src/ being used by the main source set.
        // Adding new build types or product flavors should be accompanied
        // by a similar customization.
        debug.setRoot('build-types/debug')
        release.setRoot('build-types/release')
    }
    signingConfigs {
        release {
            release {
                storeFile  file('/path/to/your/keystore')
                //leave blank to fill in later
                storePassword  ""
                keyAlias 'yourAlias'
                //leave blank to fill in later
                keyPassword  ""
            }
        }

        buildTypes {
            release {
                debuggable false
                signingConfig signingConfigs.release
            }
        }
    }
}

//signs keystore only for releases
task release << {
    android.signingConfigs.release.storePassword = new String(System.console().readPassword("\nKeystore Password: "))
    android.signingConfigs.release.keyPassword = new String(System.console().readPassword("Key Password: "))
}

//uses git tags to tag each release and keep track of version code and name
//e.g. 21v1.4.3
task tag << {
    String lastTag = 'git describe --tags'.execute().text.trim()
    def vc = lastTag.split("v")[0].toInteger()
    def vn = lastTag.split("v")[1]
    def newVersion = new String(System.console().readLine("\nEnter a new version (last: ${vn}): "))
    "git tag ${++vc}v${newVersion}".execute()
    android.defaultConfig.versionCode = vc
    android.defaultConfig.versionName = newVersion
}

tasks.whenTaskAdded { assembleRelease ->
    if (assembleRelease.name.equals("packageRelease")) {
        assembleRelease.dependsOn "release"
    }
    //only tag if keystore passes
    if (assembleRelease.name.equals("zipalignRelease")) {
        assembleRelease.dependsOn "tag"
    }
}