Place the jrubyjar and prepareJrubyJar in the right group

Fixes #357

jar-plugin/src/main/groovy/com/github/jrubygradle/jar/JRubyJar.groovy

@@ -23,6 +23,8 @@ import org.gradle.api.tasks.StopExecutionException
 import org.gradle.api.tasks.bundling.Jar
 import org.gradle.api.tasks.bundling.ZipEntryCompression
 
+import static com.github.jrubygradle.JRubyPlugin.TASK_GROUP_NAME
+
 /**
  * JRubyJar creates a Java Archive with Ruby code packed inside of it.
  *
@@ -247,7 +249,9 @@ class JRubyJar extends Jar {
         appendix = 'jruby'
         /* Make sure our default configuration is present regardless of whether we use it or not */
         prepareTask = project.task("prepare${prepareNameForSuffix(name)}", type: JRubyPrepare)
+        prepareTask.group TASK_GROUP_NAME
         dependsOn prepareTask
+        group TASK_GROUP_NAME
 
         // TODO get rid of this and try to adjust the CopySpec for the gems
         // to exclude '.jrubydir'

jar-plugin/src/test/groovy/com/github/jrubygradle/jar/JRubyJarSpec.groovy

@@ -21,6 +21,17 @@ class JRubyJarSpec extends Specification {
         }
     }
 
+    @Issue('https://github.com/jruby-gradle/jruby-gradle-plugin/issues/357')
+    void 'group should be set to "JRuby"'() {
+        given:
+        JRubyJar task = project.task('spock-jar', type: JRubyJar)
+        def prepareTask = project.tasks.find { it.name == 'prepareSpock-jar' }
+
+        expect:
+        task.group == 'JRuby'
+        prepareTask.group == task.group
+    }
+
     void "jrubyVersion should be configurable in a Gradle conventional way"() {
         given:
         final String version = '1.7.20'