Rebase on master and apply review feedback

gradle-plugins/src/integTest/groovy/com/linkedin/pegasus/gradle/PegasusPluginIntegrationTest.groovy

@@ -22,7 +22,7 @@ class PegasusPluginIntegrationTest extends Specification {
         .withProjectDir(tempDir.root)
         .withPluginClasspath()
         .withArguments('mainDataTemplateJar')
-        //.forwardOutput()
+        .forwardOutput()
         .build()
 
     then:

gradle-plugins/src/integTest/groovy/com/linkedin/pegasus/gradle/publishing/PegasusPluginIvyPublishIntegrationTest.groovy

@@ -1,3 +1,19 @@
+/*
+ * Copyright (c) 2021 LinkedIn Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package com.linkedin.pegasus.gradle.publishing
 
 import org.gradle.testkit.runner.GradleRunner

gradle-plugins/src/main/java/com/linkedin/pegasus/gradle/PegasusPlugin.java

@@ -1834,6 +1834,15 @@ protected GenerateDataTemplateTask configureDataTemplateGeneration(Project proje
     // FIXME change to #getArchiveFile(); breaks backwards-compatibility before 5.1
     project.getDependencies().add(compileConfigName, project.files(dataTemplateJarTask.getArchivePath()));
 
+    // The below Action is only applied when the 'ivy-publish' is applied by the consumer.
+    // If the consumer does not use ivy-publish, this is a noop.
+    // this Action prepares the project applying the pegasus plugin to publish artifacts using these steps:
+    // 1. Registers "feature variants" for pegasus-specific artifacts;
+    //      see https://docs.gradle.org/6.1/userguide/feature_variants.html
+    // 2. Wires legacy configurations like `dataTemplateCompile` to auto-generated feature variant *Api and
+    //      *Implementation configurations for backwards compatibility.
+    // 3. Configures the Ivy Publication to include auto-generated feature variant *Api and *Implementation
+    //      configurations and their dependencies.
     project.getPlugins().withType(IvyPublishPlugin.class, ivyPublish -> {
       if (!isAtLeastGradle61())
       {