Extract fallback update routine to pvt method

app/services/merge_requests/update_service.rb

@@ -11,22 +11,7 @@ module MergeRequests
     end
 
     def execute(merge_request)
-      updated_merge_request = update_merge_request_with_specialized_service(merge_request)
-
-      return updated_merge_request unless updated_merge_request.nil?
-
-      # We don't allow change of source/target projects and source branch
-      # after merge request was created
-      params.delete(:source_project_id)
-      params.delete(:target_project_id)
-      params.delete(:source_branch)
-
-      if merge_request.closed_or_merged_without_fork?
-        params.delete(:target_branch)
-        params.delete(:force_remove_source_branch)
-      end
-
-      update_task_event(merge_request) || update(merge_request)
+      update_merge_request_with_specialized_service(merge_request) || general_fallback(merge_request)
     end
 
     def handle_changes(merge_request, options)
@@ -90,6 +75,21 @@ module MergeRequests
 
     attr_reader :target_branch_was_deleted
 
+    def general_fallback(merge_request)
+      # We don't allow change of source/target projects and source branch
+      # after merge request was created
+      params.delete(:source_project_id)
+      params.delete(:target_project_id)
+      params.delete(:source_branch)
+
+      if merge_request.closed_or_merged_without_fork?
+        params.delete(:target_branch)
+        params.delete(:force_remove_source_branch)
+      end
+
+      update_task_event(merge_request) || update(merge_request)
+    end
+
     def track_title_and_desc_edits(changed_fields)
       tracked_fields = %w(title description)
 

ee/app/services/ee/merge_requests/update_service.rb

@@ -5,12 +5,10 @@ module EE
     module UpdateService
       extend ::Gitlab::Utils::Override
 
-      override :execute
-      def execute(merge_request)
-        updated_merge_request = update_merge_request_with_specialized_service(merge_request)
-
-        return updated_merge_request unless updated_merge_request.nil?
+      private
 
+      override :general_fallback
+      def general_fallback(merge_request)
         unless update_task_event?
           old_approvers = merge_request.overall_approvers(exclude_code_owners: true)
         end
@@ -37,8 +35,6 @@ module EE
         merge_request
       end
 
-      private
-
       override :after_update
       def after_update(merge_request)
         super