Stop deploying to pages legacy storage if feature flag is disabled

app/services/projects/update_pages_service.rb

@@ -80,6 +80,10 @@ module Projects
     end
 
     def deploy_to_legacy_storage(artifacts_path)
+      # path today used by one project can later be used by another
+      # so we can't really scope this feature flag by project or group
+      return unless Feature.enabled?(:pages_update_legacy_storage, default_enabled: true)
+
       # Create temporary directory in which we will extract the artifacts
       make_secure_tmp_dir(tmp_path) do |tmp_path|
         extract_archive!(artifacts_path, tmp_path)

config/feature_flags/development/pages_update_legacy_storage.yml

+---
+name: pages_update_legacy_storage
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/50683
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/296138
+milestone: '13.9'
+type: development
+group: group::release
+default_enabled: true

spec/services/projects/update_pages_service_spec.rb

@@ -55,6 +55,15 @@ RSpec.describe Projects::UpdatePagesService do
         end
       end
 
+      it "doesn't deploy to legacy storage if it's disabled" do
+        stub_feature_flags(pages_update_legacy_storage: false)
+
+        expect(execute).to eq(:success)
+        expect(project.pages_deployed?).to be_truthy
+
+        expect(File.exist?(File.join(project.pages_path, 'public', 'index.html'))).to eq(false)
+      end
+
       it 'creates pages_deployment and saves it in the metadata' do
         expect do
           expect(execute).to eq(:success)