Fix pipeline reference existence check and add specs

app/models/ci/pipeline.rb

@@ -269,7 +269,7 @@ module Ci
     end
 
     def ref_exists?
-      project.repository.ref_exists?(self.ref)
+      project.repository.ref_exists?(git_ref)
     end
 
     ##
@@ -678,11 +678,11 @@ module Ci
 
     def push_details
       strong_memoize(:push_details) do
-        Gitlab::Git::Push.new(project, before_sha, sha, push_ref)
+        Gitlab::Git::Push.new(project, before_sha, sha, git_ref)
       end
     end
 
-    def push_ref
+    def git_ref
       if branch?
         Gitlab::Git::BRANCH_REF_PREFIX + ref.to_s
       elsif tag?

spec/models/ci/pipeline_spec.rb

@@ -779,6 +779,29 @@ describe Ci::Pipeline, :mailer do
     end
   end
 
+  describe 'ref_exists?' do
+    using RSpec::Parameterized::TableSyntax
+
+    let(:project) { create(:project, :repository) }
+
+    where(:tag, :ref, :result) do
+      false | 'master'              | true
+      false | 'non-existent-branch' | false
+      true  | 'v1.1.0'              | true
+      true  | 'non-existent-tag'    | false
+    end
+
+    with_them do
+      let(:pipeline) do
+        create(:ci_empty_pipeline, project: project, tag: tag, ref: ref)
+      end
+
+      it "correctly detects ref" do
+        expect(pipeline.ref_exists?).to be result
+      end
+    end
+  end
+
   context 'with non-empty project' do
     let(:project) { create(:project, :repository) }