Add manifest information to the jar file's META-INF

NOTICE.txt

@@ -0,0 +1,2 @@
+Elasticsearch Java Client
+Copyright 2021 Elasticsearch B.V.

build.gradle.kts

@@ -25,8 +25,16 @@ subprojects {
     apply(plugin = "checkstyle")
 }
 
-/*
-TODO:
-- checkstyle + reformat
-- license check
- */
+val grgit = org.ajoberstar.grgit.Grgit.open(mapOf("currentDir" to project.rootDir))
+try {
+    allprojects {
+        project.extra["gitHashFull"] = grgit.head().id
+        project.extra["gitCommitTime"] = grgit.head().dateTime.withZoneSameLocal(java.time.ZoneOffset.UTC)
+    }
+} finally {
+    grgit.close()
+}
+
+allprojects {
+    project.extra["buildTime"] = java.time.Instant.now().atZone(java.time.ZoneOffset.UTC)
+}

buildSrc/build.gradle.kts

@@ -0,0 +1,26 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you 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.
+ */
+
+dependencies {
+    implementation("org.ajoberstar.grgit:grgit-gradle:4.0.1")
+}
+
+repositories {
+    maven("https://plugins.gradle.org/m2/")
+}

java-client/build.gradle.kts

@@ -31,6 +31,22 @@ java {
     sourceCompatibility = JavaVersion.VERSION_1_8
 }
 
+tasks.withType<Jar> {
+    manifest {
+        attributes["Implementation-Title"] = "Elasticsearch Java client"
+        attributes["Implementation-Vendor"] = "Elastic"
+        attributes["Implementation-URL"] = "https://github.com/elastic/elasticsearch-java/"
+        attributes["Build-Date"] = project.extra["buildTime"]
+        attributes["X-Git-Revision"] = project.extra["gitHashFull"]
+        attributes["X-Git-Commit-Time"] = project.extra["gitCommitTime"]
+    }
+
+    metaInf {
+        into(".").from("../LICENSE.txt")
+        into(".").from("../NOTICE.txt")
+    }
+}
+
 publishing {
     repositories {
         maven {