Make CI build to use optimistic locking only on status change

app/models/commit_status.rb

@@ -105,6 +105,10 @@ class CommitStatus < ActiveRecord::Base
     end
   end
 
+  def locking_enabled?
+    status_changed?
+  end
+
   def before_sha
     pipeline.before_sha || Gitlab::Git::BLANK_SHA
   end

changelogs/unreleased/make-ci-build-to-lock-on-status-change.yml

+---
+title: Make CI build to use optimistic locking only on status change
+merge_request:
+author:

spec/models/commit_status_spec.rb

@@ -297,4 +297,40 @@ describe CommitStatus, :models do
       end
     end
   end
+
+  describe '#locking_enabled?' do
+    before do
+      commit_status.lock_version = 100
+    end
+
+    subject { commit_status.locking_enabled? }
+
+    context "when changing status" do
+      before do
+        commit_status.status = "running"
+      end
+
+      it "lock" do
+        is_expected.to be true
+      end
+
+      it "raise exception when trying to update" do
+        expect{ commit_status.save }.to raise_error(ActiveRecord::StaleObjectError)
+      end
+    end
+
+    context "when changing description" do
+      before do
+        commit_status.description = "test"
+      end
+
+      it "do not lock" do
+        is_expected.to be false
+      end
+
+      it "save correctly" do
+        expect(commit_status.save).to be true
+      end
+    end
+  end
 end