Automatically update MR merge-ref along merge status

This couples the code that transitions the `MergeRequest#merge_status`
and refs/merge-requests/:iid/merge ref update.

In general, instead of directly telling `MergeToRefService` to update
the merge ref, we should rely on `MergeabilityCheckService` to keep
both the merge status and merge ref synced. Now, if the merge_status is
`can_be_merged` it means the merge-ref is also updated to the latest.

We've also updated the logic to be more systematic and less user-based.

1 files changed, 52 insertions, 0 deletions

diff --git a/spec/migrations/enqueue_reset_merge_status_second_run_spec.rb b/spec/migrations/enqueue_reset_merge_status_second_run_spec.rb
new file mode 100644
index 00000000000..3c880c6f5fd
--- /dev/null
+++ b/spec/migrations/enqueue_reset_merge_status_second_run_spec.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20190620112608_enqueue_reset_merge_status_second_run.rb')
+
+describe EnqueueResetMergeStatusSecondRun, :migration, :sidekiq do
+  let(:namespaces) { table(:namespaces) }
+  let(:projects) { table(:projects) }
+  let(:namespace) { namespaces.create(name: 'gitlab', path: 'gitlab-org') }
+  let(:project) { projects.create(namespace_id: namespace.id, name: 'foo') }
+  let(:merge_requests) { table(:merge_requests) }
+
+  def create_merge_request(id, extra_params = {})
+    params = {
+      id: id,
+      target_project_id: project.id,
+      target_branch: 'master',
+      source_project_id: project.id,
+      source_branch: 'mr name',
+      title: "mr name#{id}"
+    }.merge(extra_params)
+
+    merge_requests.create!(params)
+  end
+
+  it 'correctly schedules background migrations' do
+    create_merge_request(1, state: 'opened', merge_status: 'can_be_merged')
+    create_merge_request(2, state: 'opened', merge_status: 'can_be_merged')
+    create_merge_request(3, state: 'opened', merge_status: 'can_be_merged')
+    create_merge_request(4, state: 'merged', merge_status: 'can_be_merged')
+    create_merge_request(5, state: 'opened', merge_status: 'unchecked')
+
+    stub_const("#{described_class.name}::BATCH_SIZE", 2)
+
+    Sidekiq::Testing.fake! do
+      Timecop.freeze do
+        migrate!
+
+        expect(described_class::MIGRATION)
+          .to be_scheduled_delayed_migration(5.minutes, 1, 2)
+
+        expect(described_class::MIGRATION)
+          .to be_scheduled_delayed_migration(10.minutes, 3, 4)
+
+        expect(described_class::MIGRATION)
+          .to be_scheduled_delayed_migration(15.minutes, 5, 5)
+
+        expect(BackgroundMigrationWorker.jobs.size).to eq(3)
+      end
+    end
+  end
+end