Add feature flag enabled by default

ee/lib/ee/gitlab/git_access.rb

@@ -84,8 +84,6 @@ module EE
       def check_push_size!
         return unless check_size_limit?
 
-        git_env = ::Gitlab::Git::HookEnv.all(repository.gl_repository)
-
         # Use #quarantine_size to get correct push size whenever a lof of changes
         # gets pushed at the same time containing the same blobs. This is only
         # doable if GIT_OBJECT_DIRECTORY_RELATIVE env var is set and happens
@@ -94,13 +92,21 @@ module EE
         # Fallback to determining push size using the changes_list so we can still
         # determine the push size if env var isn't set (e.g. changes are made
         # via UI and API).
-        push_size = git_env['GIT_OBJECT_DIRECTORY_RELATIVE'].present? ? quarantine_size : changes_size
+        push_size = check_quarantine_size? ? quarantine_size : changes_size
 
         if project.changes_will_exceed_size_limit?(push_size)
           raise ::Gitlab::GitAccess::UnauthorizedError, ::Gitlab::RepositorySizeError.new(project).new_changes_error
         end
       end
 
+      def check_quarantine_size?
+        strong_memoize(:check_quarantine_size) do
+          git_env = ::Gitlab::Git::HookEnv.all(repository.gl_repository)
+
+          git_env['GIT_OBJECT_DIRECTORY_RELATIVE'].present? && ::Feature.enabled?(:quarantine_push_size_check, default_enabled: true)
+        end
+      end
+
       def quarantine_size
         project.repository.object_directory_size
       end

ee/spec/lib/gitlab/git_access_spec.rb

@@ -220,21 +220,7 @@ describe Gitlab::GitAccess do
       end
     end
 
-    context 'when GIT_OBJECT_DIRECTORY_RELATIVE env var is set' do
-      let(:object_directory_size) { 1.megabyte }
-
-      before do
-        allow(Gitlab::Git::HookEnv)
-          .to receive(:all)
-          .with(repository.gl_repository)
-          .and_return({ 'GIT_OBJECT_DIRECTORY_RELATIVE' => 'objects' })
-
-        # Stub the object directory size to "simulate" quarantine size
-        allow(repository)
-          .to receive(:object_directory_size)
-          .and_return(object_directory_size)
-      end
-
+    shared_examples_for 'a push to repository using git-rev-list for checking against repository size limit' do
       context 'when repository size is over limit' do
         let(:repository_size) { 2.megabytes }
         let(:repository_size_limit) { 1.megabyte }
@@ -248,18 +234,20 @@ describe Gitlab::GitAccess do
 
         it_behaves_like 'a push to repository below the limit'
 
-        context 'when object directory (quarantine) size exceeds the limit' do
-          let(:object_directory_size) { 2.megabytes }
-
+        context 'when new change exceeds the limit' do
           it 'rejects the push' do
+            expect(repository.new_blobs(sha_with_2_mb_file)).to be_present
+
             expect do
               push_changes("#{Gitlab::Git::BLANK_SHA} #{sha_with_2_mb_file} refs/heads/my_branch_2")
             end.to raise_error(described_class::UnauthorizedError, /Your push to this repository would cause it to exceed the size limit/)
           end
         end
 
-        context 'when object directory (quarantine) size does not exceed the limit' do
+        context 'when new change does not exceed the limit' do
           it 'accepts the push' do
+            expect(repository.new_blobs(sha_with_smallest_changes)).to be_present
+
             expect do
               push_changes("#{Gitlab::Git::BLANK_SHA} #{sha_with_smallest_changes} refs/heads/my_branch_3")
             end.not_to raise_error
@@ -268,40 +256,68 @@ describe Gitlab::GitAccess do
       end
     end
 
-    context 'when GIT_OBJECT_DIRECTORY_RELATIVE env var is not set' do
-      context 'when repository size is over limit' do
-        let(:repository_size) { 2.megabytes }
-        let(:repository_size_limit) { 1.megabyte }
-
-        it_behaves_like 'a push to repository over the limit'
+    context 'when GIT_OBJECT_DIRECTORY_RELATIVE env var is set' do
+      before do
+        allow(Gitlab::Git::HookEnv)
+          .to receive(:all)
+          .with(repository.gl_repository)
+          .and_return({ 'GIT_OBJECT_DIRECTORY_RELATIVE' => 'objects' })
       end
 
-      context 'when repository size is below the limit' do
-        let(:repository_size) { 1.megabyte }
-        let(:repository_size_limit) { 2.megabytes }
+      context 'when quarantine_push_size_check feature is enabled (default)' do
+        let(:object_directory_size) { 1.megabyte }
 
-        it_behaves_like 'a push to repository below the limit'
+        before do
+          # Stub the object directory size to "simulate" quarantine size
+          allow(repository)
+            .to receive(:object_directory_size)
+            .and_return(object_directory_size)
+        end
 
-        context 'when new change exceeds the limit' do
-          it 'rejects the push' do
-            expect(repository.new_blobs(sha_with_2_mb_file)).to be_present
+        context 'when repository size is over limit' do
+          let(:repository_size) { 2.megabytes }
+          let(:repository_size_limit) { 1.megabyte }
 
-            expect do
-              push_changes("#{Gitlab::Git::BLANK_SHA} #{sha_with_2_mb_file} refs/heads/my_branch_2")
-            end.to raise_error(described_class::UnauthorizedError, /Your push to this repository would cause it to exceed the size limit/)
-          end
+          it_behaves_like 'a push to repository over the limit'
         end
 
-        context 'when new change does not exceed the limit' do
-          it 'accepts the push' do
-            expect(repository.new_blobs(sha_with_smallest_changes)).to be_present
+        context 'when repository size is below the limit' do
+          let(:repository_size) { 1.megabyte }
+          let(:repository_size_limit) { 2.megabytes }
 
-            expect do
-              push_changes("#{Gitlab::Git::BLANK_SHA} #{sha_with_smallest_changes} refs/heads/my_branch_3")
-            end.not_to raise_error
+          it_behaves_like 'a push to repository below the limit'
+
+          context 'when object directory (quarantine) size exceeds the limit' do
+            let(:object_directory_size) { 2.megabytes }
+
+            it 'rejects the push' do
+              expect do
+                push_changes("#{Gitlab::Git::BLANK_SHA} #{sha_with_2_mb_file} refs/heads/my_branch_2")
+              end.to raise_error(described_class::UnauthorizedError, /Your push to this repository would cause it to exceed the size limit/)
+            end
+          end
+
+          context 'when object directory (quarantine) size does not exceed the limit' do
+            it 'accepts the push' do
+              expect do
+                push_changes("#{Gitlab::Git::BLANK_SHA} #{sha_with_smallest_changes} refs/heads/my_branch_3")
+              end.not_to raise_error
+            end
           end
         end
       end
+
+      context 'when quarantine_push_size_check feature is disabled' do
+        before do
+          stub_feature_flags(quarantine_push_size_check: false)
+        end
+
+        it_behaves_like 'a push to repository using git-rev-list for checking against repository size limit'
+      end
+    end
+
+    context 'when GIT_OBJECT_DIRECTORY_RELATIVE env var is not set' do
+      it_behaves_like 'a push to repository using git-rev-list for checking against repository size limit'
     end
   end