Issue #3266092: Make sure staging root is unique for each Drupal site

package_manager/src/Stage.php

@@ -44,11 +44,12 @@ use Symfony\Contracts\EventDispatcher\EventDispatcherInterface;
  * Although a site can only have one staging area, it is possible, but unlikely,
  * for privileged users to destroy a stage created by another user, then create
  * their own, new stage. To prevent such situations from putting the file system
- * into an indeterminate state, each staging area lives in its own directory
- * with a randomly generated name. For additional cleanliness, all staging areas
- * created by a specific site live in a single directory, called the "staging
- * root" and identified by the site UUID, which is deleted when any stage
- * created by that site is destroyed.
+ * into an indeterminate state (for example, if a stage is destroyed by another
+ * user while it is still being created), each staging area lives in its own
+ * directory with a randomly generated name. For additional cleanliness, all
+ * staging areas created by a specific site live in a single directory, called
+ * the "staging root" and identified by the site UUID, which is deleted when any
+ * stage created by that site is destroyed.
  */
 class Stage {
 
@@ -512,7+513,7 @@
    *
    * @return string
    *   The absolute path of the directory where changes should be staged.
    *
    * @throws \LogicException
    *   If this method is called before the stage has been created or claimed.
    */