Build: Allow build to configure which license/notice to embed in jars (#26373)

We currently add the apache license/notice for elasticsearch to any
plugin that uses our ES plugin gradle plugin. However, each plugin
should be able to use their own license. This commit adds a licenseFile
and noticeFile property to the root of project's using BuildPlugin,
which is added to jar files for that project.

build.gradle

@@ -23,6 +23,7 @@ import org.eclipse.jgit.lib.Repository
 import org.eclipse.jgit.lib.RepositoryBuilder
 import org.gradle.plugins.ide.eclipse.model.SourceFolder
 import org.apache.tools.ant.taskdefs.condition.Os
+import org.elasticsearch.gradle.BuildPlugin
 import org.elasticsearch.gradle.VersionProperties
 import org.elasticsearch.gradle.Version
 
@@ -60,6 +61,10 @@ configure(subprojects.findAll { it.projectDir.toPath().startsWith(rootPath) }) {
       }
     }
   }
+  plugins.withType(BuildPlugin).whenPluginAdded {
+    project.licenseFile = project.rootProject.file('LICENSE.txt')
+    project.noticeFile = project.rootProject.file('NOTICE.txt')
+  }
 }
 
 /* Introspect all versions of ES that may be tested agains for backwards
@@ -189,14 +194,6 @@ task branchConsistency {
 
 subprojects {
   project.afterEvaluate {
-    // include license and notice in jars
-    tasks.withType(Jar) {
-      into('META-INF') {
-        from project.rootProject.rootDir
-        include 'LICENSE.txt'
-        include 'NOTICE.txt'
-      }
-    }
     // ignore missing javadocs
     tasks.withType(Javadoc) { Javadoc javadoc ->
       // the -quiet here is because of a bug in gradle, in that adding a string option

buildSrc/src/main/groovy/org/elasticsearch/gradle/BuildPlugin.groovy

@@ -36,6 +36,7 @@ import org.gradle.api.artifacts.ModuleVersionIdentifier
 import org.gradle.api.artifacts.ProjectDependency
 import org.gradle.api.artifacts.ResolvedArtifact
 import org.gradle.api.artifacts.dsl.RepositoryHandler
+import org.gradle.api.file.CopySpec
 import org.gradle.api.plugins.JavaPlugin
 import org.gradle.api.publish.maven.MavenPublication
 import org.gradle.api.publish.maven.plugins.MavenPublishPlugin
@@ -502,6 +503,8 @@ class BuildPlugin implements Plugin<Project> {
 
     /** Adds additional manifest info to jars */
     static void configureJars(Project project) {
+        project.ext.licenseFile = null
+        project.ext.noticeFile = null
         project.tasks.withType(Jar) { Jar jarTask ->
             // we put all our distributable files under distributions
             jarTask.destinationDir = new File(project.buildDir, 'distributions')
@@ -525,6 +528,20 @@ class BuildPlugin implements Plugin<Project> {
                     jarTask.manifest.attributes('Change': 'Unknown')
                 }
             }
+            // add license/notice files
+            project.afterEvaluate {
+                if (project.licenseFile == null || project.noticeFile == null) {
+                    throw new GradleException("Must specify license and notice file for project ${project.path}")
+                }
+                jarTask.into('META-INF') {
+                    from(project.licenseFile.parent) {
+                        include project.licenseFile.name
+                    }
+                    from(project.noticeFile.parent) {
+                        include project.noticeFile.name
+                    }
+                }
+            }
         }
     }