Fix nil take regression

app/models/project.rb

@@ -1487,6 +1487,9 @@ class Project < ApplicationRecord
   end
 
   def pipeline_for(ref, sha = nil, id = nil)
+    sha ||= commit(ref).try(:sha)
+    return unless sha
+
     if id.present?
       pipelines_for(ref, sha).find_by(id: id)
     else
@@ -1494,11 +1497,7 @@ class Project < ApplicationRecord
     end
   end
 
-  def pipelines_for(ref, sha = nil)
-    sha ||= commit(ref).try(:sha)
-
-    return unless sha
-
+  def pipelines_for(ref, sha)
     ci_pipelines.order(id: :desc).where(sha: sha, ref: ref)
   end
 

spec/models/project_spec.rb

@@ -1156,7 +1156,6 @@ describe Project do
 
   describe '#pipeline_for' do
     let(:project) { create(:project, :repository) }
-    let!(:pipeline) { create_pipeline(project) }
 
     shared_examples 'giving the correct pipeline' do
       it { is_expected.to eq(pipeline) }
@@ -1168,6 +1167,9 @@ describe Project do
       end
     end
 
+    context 'with a matching pipeline' do
+      let!(:pipeline) { create_pipeline(project) }
+
       context 'with explicit sha' do
         subject { project.pipeline_for('master', pipeline.sha) }
 
@@ -1189,17 +1191,22 @@ describe Project do
       end
     end
 
+    context 'when there is no matching pipeline' do
+      subject { project.pipeline_for('master') }
+
+      it { is_expected.to be_nil }
+    end
+  end
+
   describe '#pipelines_for' do
     let(:project) { create(:project, :repository) }
     let!(:pipeline) { create_pipeline(project) }
     let!(:other_pipeline) { create_pipeline(project) }
 
-    context 'with implicit sha' do
-      subject { project.pipelines_for('master') }
+    subject { project.pipelines_for(project.default_branch, project.commit.sha) }
 
     it { is_expected.to contain_exactly(pipeline, other_pipeline) }
   end
-  end
 
   describe '#builds_enabled' do
     let(:project) { create(:project) }