Add git_push_execute_all_project_hooks flag

This flag is added so the new behavior can be disabled by enabling
it. It's disabled by default.

app/services/git/process_ref_changes_service.rb

@@ -15,10 +15,9 @@ module Git
 
     def process_changes_by_action(ref_type, changes)
       changes_by_action = group_changes_by_action(changes)
-      execute_project_hooks = changes.size <= Gitlab::CurrentSettings.push_event_hooks_limit
 
       changes_by_action.each do |_, changes|
-        process_changes(ref_type, changes, execute_project_hooks: execute_project_hooks) if changes.any?
+        process_changes(ref_type, changes, execute_project_hooks: execute_project_hooks?(changes)) if changes.any?
       end
     end
 
@@ -35,6 +34,10 @@ module Git
       :pushed
     end
 
+    def execute_project_hooks?(changes)
+      (changes.size <= Gitlab::CurrentSettings.push_event_hooks_limit) || Feature.enabled?(:git_push_execute_all_project_hooks, project)
+    end
+
     def process_changes(ref_type, changes, execute_project_hooks: true)
       push_service_class = push_service_class_for(ref_type)
 

spec/services/git/process_ref_changes_service_spec.rb

@@ -55,6 +55,11 @@ describe Git::ProcessRefChangesService do
         stub_application_setting(push_event_hooks_limit: push_event_hooks_limit)
       end
 
+      context 'git_push_execute_all_project_hooks is disabled' do
+        before do
+          stub_feature_flags(git_push_execute_all_project_hooks: false)
+        end
+
         it "calls #{push_service_class} with execute_project_hooks set to false" do
           expect(push_service_class)
             .to receive(:new)
@@ -66,6 +71,23 @@ describe Git::ProcessRefChangesService do
         end
       end
 
+      context 'git_push_execute_all_project_hooks is enabled' do
+        before do
+          stub_feature_flags(git_push_execute_all_project_hooks: true)
+        end
+
+        it "calls #{push_service_class} with execute_project_hooks set to true" do
+          expect(push_service_class)
+            .to receive(:new)
+            .with(project, project.owner, hash_including(execute_project_hooks: true))
+            .exactly(changes.count).times
+            .and_return(service)
+
+          subject.execute
+        end
+      end
+    end
+
     context 'pipeline creation' do
       context 'with valid .gitlab-ci.yml' do
         before do