Gradle get hg mercurial changeset revision

build.gradle

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.aragost.javahg:javahg:0.4'
    }
}

task revision << {
    println "Build revision: $scmRevision"
}


import com.aragost.javahg.Changeset
import com.aragost.javahg.Repository
import com.aragost.javahg.commands.ParentsCommand

String getHgRevision() {
    def repo = Repository.open(projectDir)
    def parentsCommand = new ParentsCommand(repo)
    List<Changeset> changesets = parentsCommand.execute()
    if (changesets == null || changesets.size() != 1) {
        def message = "Exactly one was parent expected. " + changesets
        throw new Exception(message)
    }
    return changesets[0].node
}

ext {
    scmRevision = getHgRevision()
}