Gradle task to include in CI job for pull requests that confirms the contribution sufficiently increments the Gradle version field

build.gradle

buildscript {
    dependencies {
        classpath "com.github.zafarkhaja:java-semver:0.9.0"
    }
}

plugins {
    id "org.ajoberstar.grgit" version "1.4.2"
}

/**
 * Task executed by Jenkins on Pull Requests to confirm the contribution has appropriately
 * incremented the gradle 'version' field above.
 */
task confirmProjectVersionIncremented() {
    doLast {
        def grgit = org.ajoberstar.grgit.Grgit.open(project.rootDir)

        def describe = grgit.describe()
        def lastVersion = com.github.zafarkhaja.semver.Version.valueOf(describe)
        if(!''.equals(lastVersion.getPreReleaseVersion())) {
            // git describe produced something like '0.20.7-1-gfbe61fd'
            // split on '-' and recreate last as the first token
            lastVersion = com.github.zafarkhaja.semver.Version.valueOf(describe.split('-')[0])
        }

        // read 'version' field from build.gradle
        def currentVersion = com.github.zafarkhaja.semver.Version.valueOf(getVersion());
        if ( currentVersion.greaterThan(lastVersion) ) {
            // success, the project version is greater than the last one available via git describe
            println "Version test successful: proposed version is " + currentVersion + " greater than last.released.version " + lastVersion
        } else {
            throw new GradleException("version field in build.gradle with current value " + currentVersion + " must be incremented past " + lastVersion)
        }
    }
}