Add link to MR from Build detail page. #3452

app/models/ci/build.rb

@@ -135,6 +135,16 @@ module Ci
       predefined_variables + yaml_variables + project_variables + trigger_variables
     end
 
+    def merge_request
+      merge_requests = MergeRequest.includes(:merge_request_diff)
+                                   .where(source_branch: ref, source_project_id: commit.gl_project_id)
+                                   .reorder(iid: :asc)
+
+      merge_requests.find do |merge_request|
+        merge_request.commits.any? { |ci| ci.id == commit.sha }
+      end
+    end
+
     def project
       commit.project
     end

app/views/projects/builds/show.html.haml

@@ -7,6 +7,10 @@
     %strong.monospace= link_to @build.commit.short_sha, ci_status_path(@build.commit)
     from
     = link_to @build.ref, namespace_project_commits_path(@project.namespace, @project, @build.ref)
+    - merge_request = @build.merge_request
+    - if merge_request
+      via
+      = link_to "merge request ##{merge_request.iid}", merge_request_path(merge_request)
 
   #up-build-trace
   - if @commit.matrix_for_ref?(@build.ref)

spec/models/build_spec.rb

@@ -390,4 +390,68 @@ describe Ci::Build, models: true do
     it { is_expected.to include('gitlab-ci-token') }
     it { is_expected.to include(project.web_url[7..-1]) }
   end
+
+  def create_mr(build, commit, factory: :merge_request, created_at: Time.now)
+    FactoryGirl.create(factory,
+                       source_project_id: commit.gl_project_id,
+                       target_project_id: commit.gl_project_id,
+                       source_branch: build.ref,
+                       created_at: created_at)
+  end
+
+  describe :merge_request do
+    context 'when a MR has a reference to the commit' do
+      before do
+        @merge_request = create_mr(build, commit, factory: :merge_request)
+
+        commits = [double(id: commit.sha)]
+        allow(@merge_request).to receive(:commits).and_return(commits)
+        allow(MergeRequest).to receive_message_chain(:includes, :where, :reorder).and_return([@merge_request])
+      end
+
+      it 'returns the single associated MR' do
+        expect(build.merge_request.id).to eq(@merge_request.id)
+      end
+    end
+
+    context 'when there is not a MR referencing the commit' do
+      it 'returns nil' do
+        expect(build.merge_request).to be_nil
+      end
+    end
+
+    context 'when more than one MR have a reference to the commit' do
+      before do
+        @merge_request = create_mr(build, commit, factory: :merge_request)
+        @merge_request.close!
+        @merge_request2 = create_mr(build, commit, factory: :merge_request)
+
+        commits = [double(id: commit.sha)]
+        allow(@merge_request).to receive(:commits).and_return(commits)
+        allow(@merge_request2).to receive(:commits).and_return(commits)
+        allow(MergeRequest).to receive_message_chain(:includes, :where, :reorder).and_return([@merge_request, @merge_request2])
+      end
+
+      it 'returns the first MR' do
+        expect(build.merge_request.id).to eq(@merge_request.id)
+      end
+    end
+
+    context 'when a Build is created after the MR' do
+      before do
+        @merge_request = create_mr(build, commit, factory: :merge_request_with_diffs)
+        commit2 = FactoryGirl.create :ci_commit, gl_project: gl_project
+        @build2 = FactoryGirl.create :ci_build, commit: commit2
+
+        commits = [double(id: commit.sha), double(id: commit2.sha)]
+        allow(@merge_request).to receive(:commits).and_return(commits)
+        allow(MergeRequest).to receive_message_chain(:includes, :where, :reorder).and_return([@merge_request])
+      end
+
+      it 'returns the current MR' do
+        expect(@build2.merge_request.id).to eq(@merge_request.id)
+      end
+    end
+
+  end
 end