Mark the referenced entities as syncing before saving

Closes #3523726

src/SimpleEntityMerge.php

@@ -5,6 +5,7 @@ namespace Drupal\simple_entity_merge;
 use Drupal\Core\Entity\EntityFieldManagerInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\SynchronizableInterface;
 use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\Core\Entity\ContentEntityType;
 
@@ -74,6 +75,9 @@ class SimpleEntityMerge {
               $reference->target_id = $entity_destination_id;
             }
           }
+          if ($referencing_entity instanceof SynchronizableInterface) {
+            $referencing_entity->setSyncing(true);
+          }
           $referencing_entity->save();
         }
       }
@@ -101,6 +105,9 @@ class SimpleEntityMerge {
                   $reference->target_id = $entity_destination_id;
                 }
               }
+              if ($referencing_entity instanceof SynchronizableInterface) {
+                $referencing_entity->setSyncing(true);
+              }
               $referencing_entity->save();
             }
           }