Resolve #3408488 "Make unknownpathexcluder accept"

Closes #3408488

package_manager/src/PathExcluder/UnknownPathExcluder.php

@@ -66,14 +66,12 @@ final class UnknownPathExcluder implements EventSubscriberInterface {
    *   See \Drupal\package_manager\ComposerInspector::validate().
    */
   public function excludeUnknownPaths(CollectPathsToExcludeEvent $event): void {
-    $known_paths = [];
-
     $web_root = $this->pathLocator->getWebRoot();
     // If the web root and project root are the same, there's nothing to do.
     if (empty($web_root)) {
       return;
     }
-    $known_paths[] = $web_root;
+    $known_paths[] = [$web_root];
 
     $project_root = $this->pathLocator->getProjectRoot();
     // To determine the scaffold files to exclude, the installed packages must
@@ -113,17 +111,16 @@ final class UnknownPathExcluder implements EventSubscriberInterface {
     // glob() flags aren't supported on all systems. We also can't use
     // \Drupal\Core\File\FileSystemInterface::scanDirectory(), because it
     // unconditionally ignores hidden files and directories.
-    $unknown_paths = [];
     $handle = opendir($project_root) ?: throw new \RuntimeException("Could not scan for files in the project root.");
     while ($entry = readdir($handle)) {
       if ($entry === '.' || $entry === '..' || in_array($entry, $known_paths, TRUE)) {
         continue;
       }
-      $unknown_paths[] = $entry;
+      // We can add the unknown path as-is, because it is relative to the
+      // project root.
+      $event->add($entry);
     }
     closedir($handle);
-
-    $event->addPathsRelativeToProjectRoot($unknown_paths);
   }
 
   /**