Adding Manifest File Build Date

megamek/build.gradle

@@ -1,3 +1,5 @@
+import java.time.LocalDateTime
+
 plugins {
     id 'application'
     id 'maven-publish'
@@ -64,9 +66,10 @@ ext {
 jar {
     archiveFileName = 'MegaMek.jar'
     manifest {
-        attributes "Main-Class": mainClassName
-        attributes 'Class-Path' : project.sourceSets.main.runtimeClasspath.files
+        attributes "Main-Class" : mainClassName
+        attributes "Class-Path" : project.sourceSets.main.runtimeClasspath.files
             .findAll { it.name.endsWith(".jar") }.collect { "${lib}/${it.name}" }.join(' ')
+        attributes "Build-Date" : LocalDateTime.now()
     }
 }
 

megamek/src/megamek/MegaMek.java

@@ -30,14 +30,19 @@
 
 import javax.swing.*;
 import java.io.*;
+import java.net.URL;
 import java.security.DigestInputStream;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.text.NumberFormat;
 import java.time.LocalDate;
+import java.time.LocalDateTime;
 import java.util.Arrays;
 import java.util.Locale;
 import java.util.Vector;
+import java.util.jar.Attributes;
+import java.util.jar.JarFile;
+import java.util.jar.Manifest;
 
 /**
  * This is the primary MegaMek class.
@@ -222,23 +227,39 @@ private static void startGUI() {
      * @return the underlying information for this launch of MegaMek
      */
     public static String getUnderlyingInformation(final String originProject) {
-        return MegaMek.getUnderlyingInformation(originProject, MMConstants.PROJECT_NAME);
+        return getUnderlyingInformation(originProject, MMConstants.PROJECT_NAME);
     }
 
     /**
      * @param originProject the launching project
      * @param currentProject the currently described project
      * @return the underlying information for this launch
      */
-    public static String getUnderlyingInformation(final String originProject, final String currentProject) {
-        return String.format("Starting %s v%s\n\tRelease Date: %s\n\tToday: %s\n\tOrigin Project: %s\n\tJava Vendor: %s\n\tJava Version: %s\n\tPlatform: %s %s (%s)\n\tSystem Locale: %s\n\tTotal memory available to %s: %,.0f GB",
-                currentProject, MMConstants.VERSION, MMConstants.RELEASE_DATE, LocalDate.now(),
-                originProject, System.getProperty("java.vendor"), System.getProperty("java.version"),
+    public static String getUnderlyingInformation(final String originProject,
+                                                  final String currentProject) {
+        final LocalDateTime buildDate = getBuildDate();
+        return String.format("Starting %s v%s\n\tBuild Date: %s\n\tRelease Date: %s\n\tToday: %s\n\tOrigin Project: %s\n\tJava Vendor: %s\n\tJava Version: %s\n\tPlatform: %s %s (%s)\n\tSystem Locale: %s\n\tTotal memory available to %s: %,.0f GB",
+                currentProject, MMConstants.VERSION, ((buildDate == null) ? "N/A" : buildDate),
+                MMConstants.RELEASE_DATE, LocalDate.now(), originProject,
+                System.getProperty("java.vendor"), System.getProperty("java.version"),
                 System.getProperty("os.name"), System.getProperty("os.version"),
                 System.getProperty("os.arch"), Locale.getDefault(), currentProject,
                 Runtime.getRuntime().maxMemory() / Math.pow(2, 30));
     }
 
+    public static @Nullable LocalDateTime getBuildDate() {
+        try {
+            final URL url = Thread.currentThread().getContextClassLoader().getResource(JarFile.MANIFEST_NAME);
+            if (url == null) {
+                return null;
+            }
+            final Attributes attributes = new Manifest(url.openStream()).getMainAttributes();
+            return LocalDateTime.parse(attributes.getValue("Build-Date"));
+        } catch (Exception ignored) {
+            return null;
+        }
+    }
+
     /**
      * This class parses the options passed into to MegaMek from the command line.
      */