Resolve #3408488 "Make unknownpathexcluder accept"

Closes #3408488

package_manager/src/PathExcluder/UnknownPathExcluder.php

@@ -80,7 +80,7 @@ final class UnknownPathExcluder implements EventSubscriberInterface {
     // and that requires Composer commands to be able to run. This intentionally
     // does not catch exceptions: failed Composer validation in the project root
     // implies that this excluder cannot function correctly.
-    // Note: the call to ComposerInspector::getInstalledPackagesList() would
+    // Note: the call to ComposerInspector::getConfig() would
     // also have triggered this, but explicitness is preferred here.
     // @see \Drupal\package_manager\StatusCheckTrait::runStatusCheck()
     $project_root = $this->pathLocator->getProjectRoot();
@@ -94,8 +94,15 @@ final class UnknownPathExcluder implements EventSubscriberInterface {
       $web_root,
       'composer.json',
       'composer.lock',
-      ...$this->getScaffoldFiles(),
     ];
+    foreach ($this->getScaffoldFiles() as $scaffold_file_path) {
+      // The web root is always included in staging operations, so we don't need
+      // to do anything special for scaffold files that live in it.
+      if (str_starts_with($scaffold_file_path, '[web-root]')) {
+        continue;
+      }
+      $always_include[] = ltrim($scaffold_file_path, '/');
+    }
 
     // Search for all files (including hidden ones) in the project root. We need
     // to use readdir() and friends here, rather than glob(), since certain
@@ -119,8 +126,9 @@ final class UnknownPathExcluder implements EventSubscriberInterface {
   /**
    * Gets the path of scaffold files, for example 'index.php' and 'robots.txt'.
    *
-   * @return array
-   *   The array of scaffold file paths.
+   * @return string[]
+   *   The paths of scaffold files provided by `drupal/core`, relative to the
+   *   project root.
    *
    * @todo Intelligently load scaffold files in https://drupal.org/i/3343802.
    */