Do not allow maintainer to push to maintain 404

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -10,7 +10,8 @@ RSpec.describe Projects::MergeRequestsController do
   let_it_be_with_reload(:project_public_with_private_builds) { create(:project, :repository, :public, :builds_private) }
 
   let(:user) { project.owner }
-  let(:merge_request) { create(:merge_request_with_diffs, target_project: project, source_project: project) }
+  let(:merge_request) { create(:merge_request_with_diffs, target_project: project, source_project: merge_request_source_project, allow_maintainer_to_push: false) }
+  let(:merge_request_source_project) { project }
 
   before do
     sign_in(user)
@@ -2073,8 +2074,6 @@ RSpec.describe Projects::MergeRequestsController do
   end
 
   describe 'POST #rebase' do
-    let(:viewer) { user }
-
     def post_rebase
       post :rebase, params: { namespace_id: project.namespace, project_id: project, id: merge_request }
     end
@@ -2085,7 +2084,7 @@ RSpec.describe Projects::MergeRequestsController do
 
     context 'successfully' do
       it 'enqeues a RebaseWorker' do
-        expect_rebase_worker_for(viewer)
+        expect_rebase_worker_for(user)
 
         post_rebase
 
@@ -2108,17 +2107,17 @@ RSpec.describe Projects::MergeRequestsController do
     context 'with a forked project' do
       let(:forked_project) { fork_project(project, fork_owner, repository: true) }
       let(:fork_owner) { create(:user) }
+      let(:merge_request_source_project) { forked_project }
 
-      before do
-        project.add_developer(fork_owner)
+      context 'user cannot push to source branch' do
+        before do
+          project.add_developer(fork_owner)
 
-        merge_request.update!(source_project: forked_project)
-        forked_project.add_reporter(user)
-      end
+          forked_project.add_reporter(user)
+        end
 
-      context 'user cannot push to source branch' do
         it 'returns 404' do
-          expect_rebase_worker_for(viewer).never
+          expect_rebase_worker_for(user).never
 
           post_rebase