Add -version and -help

src/main/java/hudson/remoting/Launcher.java

@@ -270,12 +270,31 @@ public void setNoCertificateCheck(boolean ignored) throws NoSuchAlgorithmExcepti
             depends = "-workDir")
     @Nonnull
     public boolean failIfWorkDirIsMissing = WorkDirManager.DEFAULT_FAIL_IF_WORKDIR_IS_MISSING;
+
+    /**
+     * Shows help message and then exits
+     * @since 3.36
+     */
+    @Option(name="-help",usage="Show this help message")
+    public boolean showHelp = false;
+
+    /**
+     * Shows version information and then exits
+     * @since 3.36
+     */
+    @Option(name="-version",usage="Shows the version of the remoting jar and then exits")
+    public boolean showVersion = false;
+
 
     public static void main(String... args) throws Exception {
         Launcher launcher = new Launcher();
         CmdLineParser parser = new CmdLineParser(launcher);
         try {
             parser.parseArgument(args);
+            if (launcher.showHelp && !launcher.showVersion) {
+                parser.printUsage(System.out);
+                return;
+            }
             launcher.run();
         } catch (CmdLineException e) {
             System.err.println(e.getMessage());
@@ -287,6 +306,13 @@ public static void main(String... args) throws Exception {
 
     @edu.umd.cs.findbugs.annotations.SuppressFBWarnings("DM_DEFAULT_ENCODING")    // log file, just like console output, should be in platform default encoding
     public void run() throws Exception {
+        if (showVersion) {
+            String version = Util.getVersion();
+            if(version != null) {
+                System.out.println(version);
+            }
+            return;
+        }
 
         // Create and verify working directory and logging
         // TODO: The pass-through for the JNLP mode has been added in JENKINS-39817. But we still need to keep this parameter in

src/main/java/hudson/remoting/Util.java

@@ -22,6 +22,9 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Base64;
+import java.util.Enumeration;
+import java.util.jar.JarFile;
+import java.util.jar.Manifest;
 
 /**
  * Misc. I/O utilities
@@ -160,4 +163,25 @@ static void mkdirs(@Nonnull File file) throws IOException {
         Files.createDirectories(PathUtils.fileToPath(file));
     }
 
+    static public String getVersion() {
+        String version = "unknown";
+        try {
+            Enumeration resEnum = Thread.currentThread().getContextClassLoader().getResources(JarFile.MANIFEST_NAME);
+            while (resEnum.hasMoreElements()) {
+                URL url = (URL) resEnum.nextElement();
+                try(InputStream is = url.openStream()) {
+                    if (is != null) {
+                        Manifest manifest = new Manifest(is);
+                        version = manifest.getMainAttributes().getValue("Version");
+                        if(version != null) {
+                            break;
+                        }
+                    }
+                }
+            }
+        } catch (IOException e) {
+            System.out.println("Could not access manifest");
+        }
+        return version;
+    }
 }

src/main/java/hudson/remoting/jnlp/Main.java

@@ -32,6 +32,7 @@
 import java.security.cert.CertificateFactory;
 import java.security.cert.X509Certificate;
 
+import hudson.remoting.Util;
 import org.jenkinsci.remoting.engine.WorkDirManager;
 import org.jenkinsci.remoting.util.PathUtils;
 import org.kohsuke.args4j.Option;
@@ -202,6 +203,20 @@ public class Main {
             usage="Specify the remoting protocols to attempt when instanceIdentity is provided.")
     public List<String> protocols = new ArrayList<>();
 
+    /**
+     * Shows help message and then exits
+     * @since 3.36
+     */
+    @Option(name="-help",usage="Show this help message")
+    public boolean showHelp = false;
+
+    /**
+     * Shows version information and then exits
+     * @since 3.36
+     */
+    @Option(name="-version",usage="Shows the version of the remoting jar and then exits")
+    public boolean showVersion = false;
+
     /**
      * Two mandatory parameters: secret key, and agent name.
      */
@@ -239,6 +254,13 @@ public static void _main(String[] args) throws IOException, InterruptedException
         Main m = new Main();
         CmdLineParser p = new CmdLineParser(m);
         p.parseArgument(args);
+        if (m.showHelp && !m.showVersion) {
+            p.printUsage(System.out);
+            return;
+        } else if(m.showVersion) {
+            System.out.println(Util.getVersion());
+            return;
+        }
         if(m.args.size()!=2) {
             throw new CmdLineException(p, "two arguments required, but got " + m.args, null);
         }