How to set up gradle and android studio to do release build?

I want to build android app and start signing it. For that I need to have Release version of apk. Google documentation suggests only Eclipse and ant ways to have release builds: http://developer.android.com/tools/publishing/app-signing.html#releasecompile

However I cannot find how to force gradle build release version of apk. build.gradle does not give any hints either. gradlew tasks suggests, that there is no install Release configuration, but uninstall release exists:

Install tasks
-------------
installDebug - Installs the Debug build
installTest - Installs the Test build for the Debug build
uninstallAll - Uninstall all applications.
uninstallDebug - Uninstalls the Debug build
uninstallRelease - Uninstalls the Release build
uninstallTest - Uninstalls the Test build for the Debug build

My build.gradle:

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.5.+'
    }
}
apply plugin: 'android'

repositories {
    mavenCentral()
}

dependencies {
    compile 'com.android.support:support-v4:13.0.+'
    compile files('libs/android-support-v4.jar')
    compile project(":libraries:ActionBarSherlock")
    compile project(":libraries:CollabsibleSearchMenu")
}

android {
    compileSdkVersion 18
    buildToolsVersion "18.0.1"

    defaultConfig {
        minSdkVersion 8
        targetSdkVersion 16
    }
}

What I am missing?

1. open the Build Variants pane, typically found along the lower left side of the window:

2. set debug to release
3. shift+f10 run!!

then, Android Studio will execute assembleRelease task and install xx-release.apk to your device.

in the latest version of android studio, you can just do:

./gradlew assembleRelease

or aR for short. This will produce an unsigned release apk. Building a signed apk can be done similarly or you can use Build -> Generate Signed Apk in Android Studio.

See the docs here

Here is my build.gradle for reference:

buildscript {
  repositories {
    mavenCentral()
  }
  dependencies {
    classpath 'com.android.tools.build:gradle:0.5.+'
  }
}
apply plugin: 'android'

dependencies {
  compile fileTree(dir: 'libs', include: '*.jar')
}

android {
compileSdkVersion 17
buildToolsVersion "17.0.0"

sourceSets {
    main {
        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')

}

buildTypes {
    release {

    }
}