Split huge method MergeRequests::UpdateService#execute

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/services/merge_requests/update_service.rb

@@ -35,6 +35,15 @@ module MergeRequests
           )
         end
 
+        handle_changes(merge_request)
+        merge_request.create_new_cross_references!(current_user)
+        execute_hooks(merge_request, 'update')
+      end
+
+      merge_request
+    end
+
+    def handle_changes(merge_request)
       if merge_request.previous_changes.include?('target_branch')
         create_branch_change_note(merge_request, 'target',
                                   merge_request.previous_changes['target_branch'].first,
@@ -58,12 +67,6 @@ module MergeRequests
           merge_request.previous_changes.include?('source_branch')
         merge_request.mark_as_unchecked
       end
-
-        merge_request.create_new_cross_references!(current_user)
-        execute_hooks(merge_request, 'update')
-      end
-
-      merge_request
     end
   end
 end