Issue #3001159 by Christian.wiedemann: getSourceStorage() should be part of ConfigInstallerInterface

core/lib/Drupal/Core/Config/ConfigInstaller.php

@@ -379,11 +379,7 @@ class ConfigInstaller implements ConfigInstallerInterface {
   }
 
   /**
-   * Gets the configuration storage that provides the default configuration.
-   *
-   * @return \Drupal\Core\Config\StorageInterface|null
-   *   The configuration storage that provides the default configuration.
-   *   Returns null if the source storage has not been set.
+   * {@inheritdoc}
    */
   public function getSourceStorage() {
     return $this->sourceStorage;

core/lib/Drupal/Core/Config/ConfigInstallerInterface.php

@@ -75,6 +75,15 @@ interface ConfigInstallerInterface {
    */
   public function setSourceStorage(StorageInterface $storage);
 
+  /**
+   * Gets the configuration storage that provides the default configuration.
+   *
+   * @return \Drupal\Core\Config\StorageInterface|null
+   *   The configuration storage that provides the default configuration.
+   *   Returns null if the source storage has not been set.
+   */
+  public function getSourceStorage();
+
   /**
    * Sets the status of the isSyncing flag.
    *