Tag and push an image created by gradle-docker to an alternative repository

build.gradle

// Will tag an push if the property 'dockerRepository' is defined

task buildDocker(type: Docker) {
    push = false
    applicationName = 'curriculi-service-users'
    dockerfile = file('src/main/docker/Dockerfile')

    doFirst {
        copy {
            from jar
            into stageDir
        }
    }

    doLast {
        tagTask(project.group, applicationName, version, true).execute()
    }
}

def tagTask(group, applicationName, version, push) {
    if (project.hasProperty('dockerRepository')) {

        def dockerRepository = project.dockerRepository
        def existingTag = "$group/$applicationName:$version"
        def toCreateTag = "$dockerRepository/$group/$applicationName:latest"

        return tasks.create("tag${applicationName}Image", Exec) {
            println("Creating tag $toCreateTag from $existingTag")
            commandLine 'docker', 'tag',
                    "$existingTag",
                    "$toCreateTag"
            if (push) {
                println("Pushing $toCreateTag ")
                commandLine 'docker', 'push', "$toCreateTag"
            }
        }
    }
}