Add support for two-step Gitaly Rebase RPC

The new two-step Gitaly `Rebase` RPC yields the rebase commit SHA to the
client before proceeding with the rebase.

This avoids an issue where the rebase commit SHA was returned when the
RPC had fully completed, and in some cases this would be after the Rails
`post_receive` worker services had already run. In these situations,
the merge request did not yet have its rebase_commit_sha attribute set
introducing the possibility for bugs (such as previous approvals being
reset).

https://gitlab.com/gitlab-org/gitlab-ee/issues/5966

1 files changed, 85 insertions, 0 deletions

diff --git a/spec/models/repository_spec.rb b/spec/models/repository_spec.rb
index a6c3d5756aa..9ff0f355fd4 100644
--- a/spec/models/repository_spec.rb
+++ b/spec/models/repository_spec.rb
@@ -1451,6 +1451,91 @@ describe Repository do
     end
   end
 
+  describe '#rebase' do
+    let(:merge_request) { create(:merge_request, source_branch: 'feature', target_branch: 'master', source_project: project) }
+
+    shared_examples_for 'a method that can rebase successfully' do
+      it 'returns the rebase commit sha' do
+        rebase_commit_sha = repository.rebase(user, merge_request)
+        head_sha = merge_request.source_project.repository.commit(merge_request.source_branch).sha
+
+        expect(rebase_commit_sha).to eq(head_sha)
+      end
+
+      it 'sets the `rebase_commit_sha` for the given merge request' do
+        rebase_commit_sha = repository.rebase(user, merge_request)
+
+        expect(rebase_commit_sha).not_to be_nil
+        expect(merge_request.rebase_commit_sha).to eq(rebase_commit_sha)
+      end
+    end
+
+    context 'when two_step_rebase feature is enabled' do
+      before do
+        stub_feature_flags(two_step_rebase: true)
+      end
+
+      it_behaves_like 'a method that can rebase successfully'
+
+      it 'executes the new Gitaly RPC' do
+        expect_any_instance_of(Gitlab::GitalyClient::OperationService).to receive(:rebase)
+        expect_any_instance_of(Gitlab::GitalyClient::OperationService).not_to receive(:user_rebase)
+
+        repository.rebase(user, merge_request)
+      end
+
+      describe 'rolling back the `rebase_commit_sha`' do
+        let(:new_sha) { Digest::SHA1.hexdigest('foo') }
+
+        it 'does not rollback when there are no errors' do
+          second_response = double(pre_receive_error: nil, git_error: nil)
+          mock_gitaly(second_response)
+
+          repository.rebase(user, merge_request)
+
+          expect(merge_request.reload.rebase_commit_sha).to eq(new_sha)
+        end
+
+        it 'does rollback when an error is encountered in the second step' do
+          second_response = double(pre_receive_error: 'my_error', git_error: nil)
+          mock_gitaly(second_response)
+
+          expect do
+            repository.rebase(user, merge_request)
+          end.to raise_error(Gitlab::Git::PreReceiveError)
+
+          expect(merge_request.reload.rebase_commit_sha).to be_nil
+        end
+
+        def mock_gitaly(second_response)
+          responses = [
+            double(rebase_sha: new_sha).as_null_object,
+            second_response
+          ]
+
+          expect_any_instance_of(
+            Gitaly::OperationService::Stub
+          ).to receive(:user_rebase_confirmable).and_return(responses.each)
+        end
+      end
+    end
+
+    context 'when two_step_rebase feature is disabled' do
+      before do
+        stub_feature_flags(two_step_rebase: false)
+      end
+
+      it_behaves_like 'a method that can rebase successfully'
+
+      it 'executes the deprecated Gitaly RPC' do
+        expect_any_instance_of(Gitlab::GitalyClient::OperationService).to receive(:user_rebase)
+        expect_any_instance_of(Gitlab::GitalyClient::OperationService).not_to receive(:rebase)
+
+        repository.rebase(user, merge_request)
+      end
+    end
+  end
+
   describe '#revert' do
     let(:new_image_commit) { repository.commit('33f3729a45c02fc67d00adb1b8bca394b0e761d9') }
     let(:update_image_commit) { repository.commit('2f63565e7aac07bcdadb654e253078b727143ec4') }