Add pipeline.default_branch? mehod

Helps to know if the pipeline ref matches  the project's default branch

app/models/ci/pipeline.rb

@@ -627,6 +627,10 @@ module Ci
       end
     end
 
+    def default_branch?
+      ref == project.default_branch
+    end
+
     private
 
     def ci_yaml_from_repo

spec/models/ci/pipeline_spec.rb

@@ -1968,4 +1968,34 @@ describe Ci::Pipeline, :mailer do
       end
     end
   end
+
+  describe '#default_branch?' do
+    let(:default_branch) { 'master'}
+
+    subject { pipeline.default_branch? }
+
+    before do
+      allow(project).to receive(:default_branch).and_return(default_branch)
+    end
+
+    context 'when pipeline ref is the default branch of the project' do
+      let(:pipeline) do
+        build(:ci_empty_pipeline, status: :created, project: project, ref: default_branch)
+      end
+
+      it "returns true" do
+        expect(subject).to be_truthy
+      end
+    end
+
+    context 'when pipeline ref is not the default branch of the project' do
+      let(:pipeline) do
+        build(:ci_empty_pipeline, status: :created, project: project, ref: 'another_branch')
+      end
+
+      it "returns false" do
+        expect(subject).to be_falsey
+      end
+    end
+  end
 end