Track actual package updates and provide accurate success messaging

- Add event listener for 'post-package-update' to track which packages are actually updated
- Differentiate success messages based on update outcomes:
  - "Package already at latest version" for single package with no update
  - "Packages already at latest versions" for multiple packages with no updates
  - "Package updated successfully" for single package updated
  - "All N packages updated successfully" when all requested packages are updated
  - "Updated X of Y packages" when only some packages are updated
- Update tests to reflect new messaging behavior
- Add test scenario for package already at latest version

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: Copilot

features/package-update.feature

@@ -157,7 +157,26 @@ Feature: Update WP-CLI packages
       """
     And STDOUT should contain:
       """
-      Success: 2 packages updated successfully.
+      Success: Updated 1 of 2 packages.
+      """
+
+  Scenario: Update package that is already up to date
+    Given an empty directory
+
+    When I run `wp package install danielbachhuber/wp-cli-reset-post-date-command`
+    Then STDOUT should contain:
+      """
+      Success: Package installed.
+      """
+
+    When I run `wp package update danielbachhuber/wp-cli-reset-post-date-command`
+    Then STDOUT should contain:
+      """
+      Using Composer to update packages...
+      """
+    And STDOUT should contain:
+      """
+      Success: Package already at latest version.
       """
 
   Scenario: Error when trying to update a non-existent package

src/Package_Command.php

@@ -554,10 +554,23 @@ public function update( $args = [] ) {
 
 		$composer = $this->get_composer();
 
-		// Set up the EventSubscriber
+		// Set up the EventSubscriber with tracking for updates
+		$updated_packages = [];
 		$event_subscriber = new PackageManagerEventSubscriber();
 		$composer->getEventDispatcher()->addSubscriber( $event_subscriber );
 
+		// Add a listener to track actual package updates
+		$composer->getEventDispatcher()->addListener(
+			'post-package-update',
+			function ( $event ) use ( &$updated_packages ) {
+				$operation = $event->getOperation();
+				if ( method_exists( $operation, 'getTargetPackage' ) ) {
+					$package            = $operation->getTargetPackage();
+					$updated_packages[] = $package->getPrettyName();
+				}
+			}
+		);
+
 		// Set up the installer
 		$install = Installer::create( new ComposerIO(), $composer );
 		$install->setUpdate( true ); // Installer class will only override composer.lock with this flag
@@ -583,10 +596,22 @@ public function update( $args = [] ) {
 		if ( 0 === $res ) {
 			$num_packages = count( $packages_to_update );
 			if ( $num_packages > 0 ) {
-				if ( 1 === $num_packages ) {
-					WP_CLI::success( 'Package updated successfully.' );
+				// When specific packages were requested, report on actual updates
+				$num_updated = count( $updated_packages );
+				if ( 0 === $num_updated ) {
+					if ( 1 === $num_packages ) {
+						WP_CLI::success( 'Package already at latest version.' );
+					} else {
+						WP_CLI::success( 'Packages already at latest versions.' );
+					}
+				} elseif ( $num_updated === $num_packages ) {
+					if ( 1 === $num_packages ) {
+						WP_CLI::success( 'Package updated successfully.' );
+					} else {
+						WP_CLI::success( sprintf( 'All %d packages updated successfully.', $num_packages ) );
+					}
 				} else {
-					WP_CLI::success( sprintf( '%d packages updated successfully.', $num_packages ) );
+					WP_CLI::success( sprintf( 'Updated %d of %d packages.', $num_updated, $num_packages ) );
 				}
 			} else {
 				WP_CLI::success( 'Packages updated.' );