Automatic merge of gitlab-org/gitlab-ce master

app/models/ci/build.rb

@@ -26,7 +26,8 @@ module Ci
     belongs_to :erased_by, class_name: 'User'
 
     RUNNER_FEATURES = {
-      upload_multiple_artifacts: -> (build) { build.publishes_artifacts_reports? }
+      upload_multiple_artifacts: -> (build) { build.publishes_artifacts_reports? },
+      refspecs: -> (build) { build.merge_request_ref? }
     }.freeze
 
     has_one :deployment, as: :deployable, class_name: 'Deployment'
@@ -47,7 +48,8 @@ module Ci
     delegate :terminal_specification, to: :runner_session, allow_nil: true
     delegate :gitlab_deploy_token, to: :project
     delegate :trigger_short_token, to: :trigger_request, allow_nil: true
-    delegate :merge_request_event?, to: :pipeline
+    delegate :merge_request_event?, :merge_request_ref?,
+             :legacy_detached_merge_request_pipeline?, to: :pipeline
 
     ##
     # Since Gitlab 11.5, deployments records started being created right after

app/models/ci/pipeline.rb

@@ -738,6 +738,10 @@ module Ci
       triggered_by_merge_request? && target_sha.nil?
     end
 
+    def legacy_detached_merge_request_pipeline?
+      detached_merge_request_pipeline? && !merge_request_ref?
+    end
+
     def merge_request_pipeline?
       triggered_by_merge_request? && target_sha.present?
     end
@@ -746,6 +750,10 @@ module Ci
       triggered_by_merge_request? && target_sha == merge_request.target_branch_sha
     end
 
+    def merge_request_ref?
+      MergeRequest.merge_request_ref?(ref)
+    end
+
     def matches_sha_or_source_sha?(sha)
       self.sha == sha || self.source_sha == sha
     end

app/models/merge_request.rb

@@ -1131,6 +1131,10 @@ class MergeRequest < ApplicationRecord
     "refs/#{Repository::REF_MERGE_REQUEST}/#{iid}/merge"
   end
 
+  def self.merge_request_ref?(ref)
+    ref.start_with?("refs/#{Repository::REF_MERGE_REQUEST}/")
+  end
+
   def in_locked_state
     begin
       lock_mr

app/presenters/ci/build_runner_presenter.rb

@@ -4,6 +4,7 @@ module Ci
   class BuildRunnerPresenter < SimpleDelegator
     include Gitlab::Utils::StrongMemoize
 
+    DEFAULT_GIT_DEPTH_MERGE_REQUEST = 10
     RUNNER_REMOTE_TAG_PREFIX = 'refs/tags/'.freeze
     RUNNER_REMOTE_BRANCH_PREFIX = 'refs/remotes/origin/'.freeze
 
@@ -27,6 +28,7 @@ module Ci
     def git_depth
       strong_memoize(:git_depth) do
         git_depth = variables&.find { |variable| variable[:key] == 'GIT_DEPTH' }&.dig(:value)
+        git_depth ||= DEFAULT_GIT_DEPTH_MERGE_REQUEST if merge_request_ref?
         git_depth.to_i
       end
     end
@@ -35,8 +37,9 @@ module Ci
       specs = []
 
       if git_depth > 0
-        specs << refspec_for_branch(ref) if branch? || merge_request_event?
+        specs << refspec_for_branch(ref) if branch? || legacy_detached_merge_request_pipeline?
         specs << refspec_for_tag(ref) if tag?
+        specs << refspec_for_merge_request_ref if merge_request_ref?
       else
         specs << refspec_for_branch
         specs << refspec_for_tag
@@ -83,5 +86,9 @@ module Ci
     def refspec_for_tag(ref = '*')
       "+#{Gitlab::Git::TAG_REF_PREFIX}#{ref}:#{RUNNER_REMOTE_TAG_PREFIX}#{ref}"
     end
+
+    def refspec_for_merge_request_ref
+      "+#{ref}:#{ref}"
+    end
   end
 end

app/services/merge_requests/base_service.rb

@@ -54,7 +54,7 @@ module MergeRequests
         merge_request, merge_request.project, current_user, merge_request.assignee)
     end
 
-    def create_merge_request_pipeline(merge_request, user)
+    def create_pipeline_for(merge_request, user)
       return unless Feature.enabled?(:ci_merge_request_pipeline,
                                      merge_request.source_project,
                                      default_enabled: true)
@@ -65,12 +65,24 @@ module MergeRequests
       return if merge_request.merge_request_pipeline_exists?
       return if merge_request.has_no_commits?
 
-      Ci::CreatePipelineService
-        .new(merge_request.source_project, user, ref: merge_request.source_branch)
-        .execute(:merge_request_event,
-                 ignore_skip_ci: true,
-                 save_on_errors: false,
-                 merge_request: merge_request)
+      create_detached_merge_request_pipeline(merge_request, user)
+    end
+
+    def create_detached_merge_request_pipeline(merge_request, user)
+      if can_use_merge_request_ref?(merge_request)
+        Ci::CreatePipelineService.new(merge_request.source_project, user,
+                                      ref: merge_request.ref_path)
+          .execute(:merge_request_event, merge_request: merge_request)
+      else
+        Ci::CreatePipelineService.new(merge_request.source_project, user,
+                                      ref: merge_request.source_branch)
+          .execute(:merge_request_event, merge_request: merge_request)
+      end
+    end
+
+    def can_use_merge_request_ref?(merge_request)
+      Feature.enabled?(:ci_use_merge_request_ref, project, default_enabled: true) &&
+        !merge_request.for_fork?
     end
 
     # Returns all origin and fork merge requests from `@project` satisfying passed arguments.

app/services/merge_requests/create_service.rb

@@ -25,7 +25,7 @@ module MergeRequests
     def after_create(issuable)
       todo_service.new_merge_request(issuable, current_user)
       issuable.cache_merge_request_closes_issues!(current_user)
-      create_merge_request_pipeline(issuable, current_user)
+      create_pipeline_for(issuable, current_user)
       issuable.update_head_pipeline
 
       super

app/services/merge_requests/refresh_service.rb

@@ -107,7 +107,7 @@ module MergeRequests
         end
 
         merge_request.mark_as_unchecked
-        create_merge_request_pipeline(merge_request, current_user)
+        create_pipeline_for(merge_request, current_user)
         UpdateHeadPipelineForMergeRequestWorker.perform_async(merge_request.id)
       end
 

changelogs/unreleased/persist-fulll-ref-path-for-mr-pipelines.yml

+---
+title: Create MR pipelines with `refs/merge-requests/:iid/head`
+merge_request: 25504
+author:
+type: changed

lib/gitlab/ci/pipeline/chain/command.rb

@@ -33,6 +33,13 @@ module Gitlab
             end
           end
 
+          def merge_request_ref_exists?
+            strong_memoize(:merge_request_ref_exists) do
+              MergeRequest.merge_request_ref?(origin_ref) &&
+                project.repository.ref_exists?(origin_ref)
+            end
+          end
+
           def ref
             strong_memoize(:ref) do
               Gitlab::Git.ref_name(origin_ref)

lib/gitlab/ci/pipeline/chain/validate/abilities.rb

@@ -44,6 +44,8 @@ module Gitlab
                 access.can_update_branch?(@command.ref)
               elsif @command.tag_exists?
                 access.can_create_tag?(@command.ref)
+              elsif @command.merge_request_ref_exists?
+                access.can_update_branch?(@command.merge_request.source_branch)
               else
                 true # Allow it for now and we'll reject when we check ref existence
               end

lib/gitlab/ci/pipeline/chain/validate/repository.rb

@@ -9,7 +9,7 @@ module Gitlab
             include Chain::Helpers
 
             def perform!
-              unless @command.branch_exists? || @command.tag_exists?
+              unless @command.branch_exists? || @command.tag_exists? || @command.merge_request_ref_exists?
                 return error('Reference not found')
               end
 

spec/factories/merge_requests.rb

@@ -117,9 +117,20 @@ FactoryBot.define do
       end
     end
 
+    trait :with_legacy_detached_merge_request_pipeline do
+      after(:create) do |merge_request|
+        merge_request.merge_request_pipelines << create(:ci_pipeline,
+          source: :merge_request_event,
+          merge_request: merge_request,
+          project: merge_request.source_project,
+          ref: merge_request.source_branch,
+          sha: merge_request.source_branch_sha)
+      end
+    end
+
     trait :with_detached_merge_request_pipeline do
-      after(:build) do |merge_request|
-        merge_request.merge_request_pipelines << build(:ci_pipeline,
+      after(:create) do |merge_request|
+        merge_request.merge_request_pipelines << create(:ci_pipeline,
           source: :merge_request_event,
           merge_request: merge_request,
           project: merge_request.source_project,
@@ -135,7 +146,7 @@ FactoryBot.define do
         target_sha { target_branch_sha }
       end
 
-      after(:build) do |merge_request, evaluator|
+      after(:create) do |merge_request, evaluator|
         merge_request.merge_request_pipelines << create(:ci_pipeline,
           source: :merge_request_event,
           merge_request: merge_request,

spec/lib/gitlab/ci/pipeline/chain/command_spec.rb

@@ -48,6 +48,24 @@ describe Gitlab::Ci::Pipeline::Chain::Command do
       end
     end
 
+    describe '#merge_request_ref_exists?' do
+      subject { command.merge_request_ref_exists? }
+
+      let!(:merge_request) { create(:merge_request, source_project: project, target_project: project) }
+
+      context 'for existing merge request ref' do
+        let(:origin_ref) { merge_request.ref_path }
+
+        it { is_expected.to eq(true) }
+      end
+
+      context 'for branch ref' do
+        let(:origin_ref) { merge_request.source_branch }
+
+        it { is_expected.to eq(false) }
+      end
+    end
+
     describe '#ref' do
       subject { command.ref }
 

spec/lib/gitlab/ci/pipeline/chain/validate/abilities_spec.rb

@@ -10,12 +10,33 @@ describe Gitlab::Ci::Pipeline::Chain::Validate::Abilities do
 
   let(:command) do
     Gitlab::Ci::Pipeline::Chain::Command.new(
-      project: project, current_user: user, origin_ref: ref)
+      project: project, current_user: user, origin_ref: origin_ref, merge_request: merge_request)
   end
 
   let(:step) { described_class.new(pipeline, command) }
 
   let(:ref) { 'master' }
+  let(:origin_ref) { ref }
+  let(:merge_request) { nil }
+
+  shared_context 'detached merge request pipeline' do
+    let(:merge_request) do
+      create(:merge_request,
+        source_project: project,
+        source_branch: ref,
+        target_project: project,
+        target_branch: 'feature')
+    end
+
+    let(:pipeline) do
+      build(:ci_pipeline,
+        source: :merge_request_event,
+        merge_request: merge_request,
+        project: project)
+    end
+
+    let(:origin_ref) { merge_request.ref_path }
+  end
 
   context 'when users has no ability to run a pipeline' do
     before do
@@ -58,6 +79,12 @@ describe Gitlab::Ci::Pipeline::Chain::Validate::Abilities do
 
       it { is_expected.to be_truthy }
 
+      context 'when pipeline is a detached merge request pipeline' do
+        include_context 'detached merge request pipeline'
+
+        it { is_expected.to be_truthy }
+      end
+
       context 'when the branch is protected' do
         let!(:protected_branch) do
           create(:protected_branch, project: project, name: ref)
@@ -65,6 +92,12 @@ describe Gitlab::Ci::Pipeline::Chain::Validate::Abilities do
 
         it { is_expected.to be_falsey }
 
+        context 'when pipeline is a detached merge request pipeline' do
+          include_context 'detached merge request pipeline'
+
+          it { is_expected.to be_falsey }
+        end
+
         context 'when developers are allowed to merge' do
           let!(:protected_branch) do
             create(:protected_branch,
@@ -74,6 +107,12 @@ describe Gitlab::Ci::Pipeline::Chain::Validate::Abilities do
           end
 
           it { is_expected.to be_truthy }
+
+          context 'when pipeline is a detached merge request pipeline' do
+            include_context 'detached merge request pipeline'
+
+            it { is_expected.to be_truthy }
+          end
         end
       end
 
@@ -112,6 +151,12 @@ describe Gitlab::Ci::Pipeline::Chain::Validate::Abilities do
         end
 
         it { is_expected.to be_truthy }
+
+        context 'when pipeline is a detached merge request pipeline' do
+          include_context 'detached merge request pipeline'
+
+          it { is_expected.to be_truthy }
+        end
       end
 
       context 'when the tag is protected' do

spec/lib/gitlab/ci/pipeline/chain/validate/repository_spec.rb

@@ -42,6 +42,25 @@ describe Gitlab::Ci::Pipeline::Chain::Validate::Repository do
     end
   end
 
+  context 'when origin ref is a merge request ref' do
+    let(:command) do
+      Gitlab::Ci::Pipeline::Chain::Command.new(
+        project: project, current_user: user, origin_ref: origin_ref, checkout_sha: checkout_sha)
+    end
+
+    let(:merge_request) { create(:merge_request, source_project: project, target_project: project) }
+    let(:origin_ref) { merge_request.ref_path }
+    let(:checkout_sha) { project.repository.commit(merge_request.ref_path).id }
+
+    it 'does not break the chain' do
+      expect(step.break?).to be false
+    end
+
+    it 'does not append pipeline errors' do
+      expect(pipeline.errors).to be_empty
+    end
+  end
+
   context 'when ref is ambiguous' do
     let(:project) do
       create(:project, :repository).tap do |proj|

spec/migrations/migrate_cluster_configure_worker_sidekiq_queue_spec.rb

@@ -3,12 +3,13 @@ require Rails.root.join('db', 'post_migrate', '20181219145520_migrate_cluster_co
 
 describe MigrateClusterConfigureWorkerSidekiqQueue, :sidekiq, :redis do
   include Gitlab::Database::MigrationHelpers
+  include StubWorker
 
   context 'when there are jobs in the queue' do
     it 'correctly migrates queue when migrating up' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'gcp_cluster:cluster_platform_configure').perform_async('Something', [1])
-        stubbed_worker(queue: 'gcp_cluster:cluster_configure').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_platform_configure').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_configure').perform_async('Something', [1])
 
         described_class.new.up
 
@@ -19,12 +20,12 @@ describe MigrateClusterConfigureWorkerSidekiqQueue, :sidekiq, :redis do
 
     it 'does not affect other queues under the same namespace' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'gcp_cluster:cluster_install_app').perform_async('Something', [1])
-        stubbed_worker(queue: 'gcp_cluster:cluster_provision').perform_async('Something', [1])
-        stubbed_worker(queue: 'gcp_cluster:cluster_wait_for_app_installation').perform_async('Something', [1])
-        stubbed_worker(queue: 'gcp_cluster:wait_for_cluster_creation').perform_async('Something', [1])
-        stubbed_worker(queue: 'gcp_cluster:cluster_wait_for_ingress_ip_address').perform_async('Something', [1])
-        stubbed_worker(queue: 'gcp_cluster:cluster_project_configure').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_install_app').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_provision').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_wait_for_app_installation').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:wait_for_cluster_creation').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_wait_for_ingress_ip_address').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_project_configure').perform_async('Something', [1])
 
         described_class.new.up
 
@@ -39,7 +40,7 @@ describe MigrateClusterConfigureWorkerSidekiqQueue, :sidekiq, :redis do
 
     it 'correctly migrates queue when migrating down' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'gcp_cluster:cluster_configure').perform_async('Something', [1])
+        stub_worker(queue: 'gcp_cluster:cluster_configure').perform_async('Something', [1])
 
         described_class.new.down
 
@@ -58,11 +59,4 @@ describe MigrateClusterConfigureWorkerSidekiqQueue, :sidekiq, :redis do
       expect { described_class.new.down }.not_to raise_error
     end
   end
-
-  def stubbed_worker(queue:)
-    Class.new do
-      include Sidekiq::Worker
-      sidekiq_options queue: queue
-    end
-  end
 end

spec/migrations/migrate_create_trace_artifact_sidekiq_queue_spec.rb

@@ -3,12 +3,13 @@ require Rails.root.join('db', 'post_migrate', '20180306074045_migrate_create_tra
 
 describe MigrateCreateTraceArtifactSidekiqQueue, :sidekiq, :redis do
   include Gitlab::Database::MigrationHelpers
+  include StubWorker
 
   context 'when there are jobs in the queues' do
     it 'correctly migrates queue when migrating up' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'pipeline_default:create_trace_artifact').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_background:archive_trace').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:create_trace_artifact').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_background:archive_trace').perform_async('Something', [1])
 
         described_class.new.up
 
@@ -19,11 +20,11 @@ describe MigrateCreateTraceArtifactSidekiqQueue, :sidekiq, :redis do
 
     it 'does not affect other queues under the same namespace' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'pipeline_default:build_coverage').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_default:build_trace_sections').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_default:pipeline_metrics').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_default:pipeline_notification').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_default:update_head_pipeline_for_merge_request').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:build_coverage').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:build_trace_sections').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:pipeline_metrics').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:pipeline_notification').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:update_head_pipeline_for_merge_request').perform_async('Something', [1])
 
         described_class.new.up
 
@@ -37,7 +38,7 @@ describe MigrateCreateTraceArtifactSidekiqQueue, :sidekiq, :redis do
 
     it 'correctly migrates queue when migrating down' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'pipeline_background:archive_trace').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_background:archive_trace').perform_async('Something', [1])
 
         described_class.new.down
 
@@ -56,11 +57,4 @@ describe MigrateCreateTraceArtifactSidekiqQueue, :sidekiq, :redis do
       expect { described_class.new.down }.not_to raise_error
     end
   end
-
-  def stubbed_worker(queue:)
-    Class.new do
-      include Sidekiq::Worker
-      sidekiq_options queue: queue
-    end
-  end
 end

spec/migrations/migrate_object_storage_upload_sidekiq_queue_spec.rb

@@ -3,12 +3,13 @@ require Rails.root.join('db', 'post_migrate', '20180603190921_migrate_object_sto
 
 describe MigrateObjectStorageUploadSidekiqQueue, :sidekiq, :redis do
   include Gitlab::Database::MigrationHelpers
+  include StubWorker
 
   context 'when there are jobs in the queue' do
     it 'correctly migrates queue when migrating up' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'object_storage_upload').perform_async('Something', [1])
-        stubbed_worker(queue: 'object_storage:object_storage_background_move').perform_async('Something', [1])
+        stub_worker(queue: 'object_storage_upload').perform_async('Something', [1])
+        stub_worker(queue: 'object_storage:object_storage_background_move').perform_async('Something', [1])
 
         described_class.new.up
 
@@ -23,11 +24,4 @@ describe MigrateObjectStorageUploadSidekiqQueue, :sidekiq, :redis do
       expect { described_class.new.up }.not_to raise_error
     end
   end
-
-  def stubbed_worker(queue:)
-    Class.new do
-      include Sidekiq::Worker
-      sidekiq_options queue: queue
-    end
-  end
 end

spec/migrations/migrate_pipeline_sidekiq_queues_spec.rb

@@ -3,12 +3,13 @@ require Rails.root.join('db', 'post_migrate', '20170822101017_migrate_pipeline_s
 
 describe MigratePipelineSidekiqQueues, :sidekiq, :redis do
   include Gitlab::Database::MigrationHelpers
+  include StubWorker
 
   context 'when there are jobs in the queues' do
     it 'correctly migrates queue when migrating up' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: :pipeline).perform_async('Something', [1])
-        stubbed_worker(queue: :build).perform_async('Something', [1])
+        stub_worker(queue: :pipeline).perform_async('Something', [1])
+        stub_worker(queue: :build).perform_async('Something', [1])
 
         described_class.new.up
 
@@ -20,10 +21,10 @@ describe MigratePipelineSidekiqQueues, :sidekiq, :redis do
 
     it 'correctly migrates queue when migrating down' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: :pipeline_default).perform_async('Class', [1])
-        stubbed_worker(queue: :pipeline_processing).perform_async('Class', [2])
-        stubbed_worker(queue: :pipeline_hooks).perform_async('Class', [3])
-        stubbed_worker(queue: :pipeline_cache).perform_async('Class', [4])
+        stub_worker(queue: :pipeline_default).perform_async('Class', [1])
+        stub_worker(queue: :pipeline_processing).perform_async('Class', [2])
+        stub_worker(queue: :pipeline_hooks).perform_async('Class', [3])
+        stub_worker(queue: :pipeline_cache).perform_async('Class', [4])
 
         described_class.new.down
 
@@ -45,11 +46,4 @@ describe MigratePipelineSidekiqQueues, :sidekiq, :redis do
       expect { described_class.new.down }.not_to raise_error
     end
   end
-
-  def stubbed_worker(queue:)
-    Class.new do
-      include Sidekiq::Worker
-      sidekiq_options queue: queue
-    end
-  end
 end

spec/migrations/migrate_storage_migrator_sidekiq_queue_spec.rb

@@ -3,11 +3,12 @@ require Rails.root.join('db', 'post_migrate', '20190124200344_migrate_storage_mi
 
 describe MigrateStorageMigratorSidekiqQueue, :sidekiq, :redis do
   include Gitlab::Database::MigrationHelpers
+  include StubWorker
 
   context 'when there are jobs in the queues' do
     it 'correctly migrates queue when migrating up' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: :storage_migrator).perform_async(1, 5)
+        stub_worker(queue: :storage_migrator).perform_async(1, 5)
 
         described_class.new.up
 
@@ -18,7 +19,7 @@ describe MigrateStorageMigratorSidekiqQueue, :sidekiq, :redis do
 
     it 'correctly migrates queue when migrating down' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: :'hashed_storage:hashed_storage_migrator').perform_async(1, 5)
+        stub_worker(queue: :'hashed_storage:hashed_storage_migrator').perform_async(1, 5)
 
         described_class.new.down
 
@@ -37,11 +38,4 @@ describe MigrateStorageMigratorSidekiqQueue, :sidekiq, :redis do
       expect { described_class.new.down }.not_to raise_error
     end
   end
-
-  def stubbed_worker(queue:)
-    Class.new do
-      include Sidekiq::Worker
-      sidekiq_options queue: queue
-    end
-  end
 end

spec/migrations/migrate_update_head_pipeline_for_merge_request_sidekiq_queue_spec.rb

@@ -3,12 +3,13 @@ require Rails.root.join('db', 'post_migrate', '20180307012445_migrate_update_hea
 
 describe MigrateUpdateHeadPipelineForMergeRequestSidekiqQueue, :sidekiq, :redis do
   include Gitlab::Database::MigrationHelpers
+  include StubWorker
 
   context 'when there are jobs in the queues' do
     it 'correctly migrates queue when migrating up' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'pipeline_default:update_head_pipeline_for_merge_request').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_processing:update_head_pipeline_for_merge_request').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:update_head_pipeline_for_merge_request').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_processing:update_head_pipeline_for_merge_request').perform_async('Something', [1])
 
         described_class.new.up
 
@@ -19,10 +20,10 @@ describe MigrateUpdateHeadPipelineForMergeRequestSidekiqQueue, :sidekiq, :redis
 
     it 'does not affect other queues under the same namespace' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'pipeline_default:build_coverage').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_default:build_trace_sections').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_default:pipeline_metrics').perform_async('Something', [1])
-        stubbed_worker(queue: 'pipeline_default:pipeline_notification').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:build_coverage').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:build_trace_sections').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:pipeline_metrics').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_default:pipeline_notification').perform_async('Something', [1])
 
         described_class.new.up
 
@@ -35,7 +36,7 @@ describe MigrateUpdateHeadPipelineForMergeRequestSidekiqQueue, :sidekiq, :redis
 
     it 'correctly migrates queue when migrating down' do
       Sidekiq::Testing.disable! do
-        stubbed_worker(queue: 'pipeline_processing:update_head_pipeline_for_merge_request').perform_async('Something', [1])
+        stub_worker(queue: 'pipeline_processing:update_head_pipeline_for_merge_request').perform_async('Something', [1])
 
         described_class.new.down
 
@@ -54,11 +55,4 @@ describe MigrateUpdateHeadPipelineForMergeRequestSidekiqQueue, :sidekiq, :redis
       expect { described_class.new.down }.not_to raise_error
     end
   end
-
-  def stubbed_worker(queue:)
-    Class.new do
-      include Sidekiq::Worker
-      sidekiq_options queue: queue
-    end
-  end
 end

spec/models/ci/build_spec.rb

@@ -25,6 +25,8 @@ describe Ci::Build do
   it { is_expected.to respond_to(:has_trace?) }
   it { is_expected.to respond_to(:trace) }
   it { is_expected.to delegate_method(:merge_request_event?).to(:pipeline) }
+  it { is_expected.to delegate_method(:merge_request_ref?).to(:pipeline) }
+  it { is_expected.to delegate_method(:legacy_detached_merge_request_pipeline?).to(:pipeline) }
 
   it { is_expected.to be_a(ArtifactMigratable) }
 
@@ -3627,6 +3629,24 @@ describe Ci::Build do
         it { is_expected.to be_falsey }
       end
     end
+
+    context 'when refspecs feature is required by build' do
+      before do
+        allow(build).to receive(:merge_request_ref?) { true }
+      end
+
+      context 'when runner provides given feature' do
+        let(:runner_features) { { refspecs: true } }
+
+        it { is_expected.to be_truthy }
+      end
+
+      context 'when runner does not provide given feature' do
+        let(:runner_features) { {} }
+
+        it { is_expected.to be_falsey }
+      end
+    end
   end
 
   describe '#deployment_status' do

spec/models/ci/pipeline_spec.rb

@@ -366,6 +366,42 @@ describe Ci::Pipeline, :mailer do
     end
   end
 
+  describe '#merge_request_ref?' do
+    subject { pipeline.merge_request_ref? }
+
+    it 'calls MergeRequest#merge_request_ref?' do
+      expect(MergeRequest).to receive(:merge_request_ref?).with(pipeline.ref)
+
+      subject
+    end
+  end
+
+  describe '#legacy_detached_merge_request_pipeline?' do
+    subject { pipeline.legacy_detached_merge_request_pipeline? }
+
+    set(:merge_request) { create(:merge_request) }
+    let(:ref) { 'feature' }
+    let(:target_sha) { nil }
+
+    let(:pipeline) do
+      build(:ci_pipeline, source: :merge_request_event, merge_request: merge_request, ref: ref, target_sha: target_sha)
+    end
+
+    it { is_expected.to be_truthy }
+
+    context 'when pipeline ref is a merge request ref' do
+      let(:ref) { 'refs/merge-requests/1/head' }
+
+      it { is_expected.to be_falsy }
+    end
+
+    context 'when target sha is set' do
+      let(:target_sha) { 'target-sha' }
+
+      it { is_expected.to be_falsy }
+    end
+  end
+
   describe '#matches_sha_or_source_sha?' do
     subject { pipeline.matches_sha_or_source_sha?(sample_sha) }
 

spec/models/merge_request_spec.rb

@@ -3114,4 +3114,32 @@ describe MergeRequest do
       end
     end
   end
+
+  describe '.merge_request_ref?' do
+    subject { described_class.merge_request_ref?(ref) }
+
+    context 'when ref is ref name of a branch' do
+      let(:ref) { 'feature' }
+
+      it { is_expected.to be_falsey }
+    end
+
+    context 'when ref is HEAD ref path of a branch' do
+      let(:ref) { 'refs/heads/feature' }
+
+      it { is_expected.to be_falsey }
+    end
+
+    context 'when ref is HEAD ref path of a merge request' do
+      let(:ref) { 'refs/merge-requests/1/head' }
+
+      it { is_expected.to be_truthy }
+    end
+
+    context 'when ref is merge ref path of a merge request' do
+      let(:ref) { 'refs/merge-requests/1/merge' }
+
+      it { is_expected.to be_truthy }
+    end
+  end
 end

spec/presenters/ci/build_runner_presenter_spec.rb

@@ -136,6 +136,24 @@ describe Ci::BuildRunnerPresenter do
         is_expected.to eq(1)
       end
     end
+
+    context 'when pipeline is detached merge request pipeline' do
+      let(:merge_request) { create(:merge_request, :with_detached_merge_request_pipeline) }
+      let(:pipeline) { merge_request.all_pipelines.first }
+      let(:build) { create(:ci_build, ref: pipeline.ref, pipeline: pipeline) }
+
+      it 'returns the default git depth for pipelines for merge requests' do
+        is_expected.to eq(described_class::DEFAULT_GIT_DEPTH_MERGE_REQUEST)
+      end
+
+      context 'when pipeline is legacy detached merge request pipeline' do
+        let(:merge_request) { create(:merge_request, :with_legacy_detached_merge_request_pipeline) }
+
+        it 'behaves as branch pipeline' do
+          is_expected.to eq(0)
+        end
+      end
+    end
   end
 
   describe '#refspecs' do
@@ -165,5 +183,25 @@ describe Ci::BuildRunnerPresenter do
         end
       end
     end
+
+    context 'when pipeline is detached merge request pipeline' do
+      let(:merge_request) { create(:merge_request, :with_detached_merge_request_pipeline) }
+      let(:pipeline) { merge_request.all_pipelines.first }
+      let(:build) { create(:ci_build, ref: pipeline.ref, pipeline: pipeline) }
+
+      it 'returns the correct refspecs' do
+        is_expected
+          .to contain_exactly('+refs/merge-requests/1/head:refs/merge-requests/1/head')
+      end
+
+      context 'when pipeline is legacy detached merge request pipeline' do
+        let(:merge_request) { create(:merge_request, :with_legacy_detached_merge_request_pipeline) }
+
+        it 'returns the correct refspecs' do
+          is_expected.to contain_exactly('+refs/tags/*:refs/tags/*',
+                                         '+refs/heads/*:refs/remotes/origin/*')
+        end
+      end
+    end
   end
 end

spec/services/merge_requests/create_service_spec.rb

@@ -173,7 +173,7 @@ describe MergeRequests::CreateService do
         end
       end
 
-      describe 'Merge request pipelines' do
+      describe 'Pipelines for merge requests' do
         before do
           stub_ci_pipeline_yaml_file(YAML.dump(config))
         end
@@ -189,12 +189,46 @@ describe MergeRequests::CreateService do
             }
           end
 
-          it 'creates a merge request pipeline and sets it as a head pipeline' do
+          it 'creates a detached merge request pipeline and sets it as a head pipeline' do
             expect(merge_request).to be_persisted
 
             merge_request.reload
             expect(merge_request.merge_request_pipelines.count).to eq(1)
-            expect(merge_request.actual_head_pipeline).to be_merge_request_event
+            expect(merge_request.actual_head_pipeline).to be_detached_merge_request_pipeline
+          end
+
+          context 'when merge request is submitted from forked project' do
+            let(:target_project) { fork_project(project, nil, repository: true) }
+
+            let(:opts) do
+              {
+                title: 'Awesome merge_request',
+                source_branch: 'feature',
+                target_branch: 'master',
+                target_project_id: target_project.id
+              }
+            end
+
+            before do
+              target_project.add_developer(assignee)
+              target_project.add_maintainer(user)
+            end
+
+            it 'create legacy detached merge request pipeline for fork merge request' do
+              expect(merge_request.actual_head_pipeline)
+                .to be_legacy_detached_merge_request_pipeline
+            end
+          end
+
+          context 'when ci_use_merge_request_ref feature flag is false' do
+            before do
+              stub_feature_flags(ci_use_merge_request_ref: false)
+            end
+
+            it 'create legacy detached merge request pipeline for non-fork merge request' do
+              expect(merge_request.actual_head_pipeline)
+                .to be_legacy_detached_merge_request_pipeline
+            end
           end
 
           context 'when there are no commits between source branch and target branch' do
@@ -207,7 +241,7 @@ describe MergeRequests::CreateService do
               }
             end
 
-            it 'does not create a merge request pipeline' do
+            it 'does not create a detached merge request pipeline' do
               expect(merge_request).to be_persisted
 
               merge_request.reload
@@ -225,7 +259,7 @@ describe MergeRequests::CreateService do
               merge_request
             end
 
-            it 'sets the latest merge request pipeline as the head pipeline' do
+            it 'sets the latest detached merge request pipeline as the head pipeline' do
               expect(merge_request.actual_head_pipeline).to be_merge_request_event
             end
           end
@@ -235,7 +269,7 @@ describe MergeRequests::CreateService do
               stub_feature_flags(ci_merge_request_pipeline: false)
             end
 
-            it 'does not create a merge request pipeline' do
+            it 'does not create a detached merge request pipeline' do
               expect(merge_request).to be_persisted
 
               merge_request.reload
@@ -254,7 +288,7 @@ describe MergeRequests::CreateService do
             }
           end
 
-          it 'does not create a merge request pipeline' do
+          it 'does not create a detached merge request pipeline' do
             expect(merge_request).to be_persisted
 
             merge_request.reload

spec/services/merge_requests/refresh_service_spec.rb

@@ -147,7 +147,7 @@ describe MergeRequests::RefreshService do
       end
     end
 
-    describe 'Merge request pipelines' do
+    describe 'Pipelines for merge requests' do
       before do
         stub_ci_pipeline_yaml_file(YAML.dump(config))
       end
@@ -165,7 +165,7 @@ describe MergeRequests::RefreshService do
           }
         end
 
-        it 'create merge request pipeline with commits' do
+        it 'create detached merge request pipeline with commits' do
           expect { subject }
             .to change { @merge_request.merge_request_pipelines.count }.by(1)
             .and change { @fork_merge_request.merge_request_pipelines.count }.by(1)
@@ -176,7 +176,34 @@ describe MergeRequests::RefreshService do
           expect(@another_merge_request.has_commits?).to be_falsy
         end
 
-        context "when branch pipeline was created before a merge request pipline has been created" do
+        it 'create detached merge request pipeline for non-fork merge request' do
+          subject
+
+          expect(@merge_request.merge_request_pipelines.first)
+            .to be_detached_merge_request_pipeline
+        end
+
+        it 'create legacy detached merge request pipeline for fork merge request' do
+          subject
+
+          expect(@fork_merge_request.merge_request_pipelines.first)
+            .to be_legacy_detached_merge_request_pipeline
+        end
+
+        context 'when ci_use_merge_request_ref feature flag is false' do
+          before do
+            stub_feature_flags(ci_use_merge_request_ref: false)
+          end
+
+          it 'create legacy detached merge request pipeline for non-fork merge request' do
+            subject
+
+            expect(@merge_request.merge_request_pipelines.first)
+              .to be_legacy_detached_merge_request_pipeline
+          end
+        end
+
+        context "when branch pipeline was created before a detaced merge request pipeline has been created" do
           before do
             create(:ci_pipeline, project: @merge_request.source_project,
                                  sha: @merge_request.diff_head_sha,
@@ -186,7 +213,7 @@ describe MergeRequests::RefreshService do
             subject
           end
 
-          it 'sets the latest merge request pipeline as a head pipeline' do
+          it 'sets the latest detached merge request pipeline as a head pipeline' do
             @merge_request.reload
             expect(@merge_request.actual_head_pipeline).to be_merge_request_event
           end
@@ -199,7 +226,7 @@ describe MergeRequests::RefreshService do
         end
 
         context "when MergeRequestUpdateWorker is retried by an exception" do
-          it 'does not re-create a duplicate merge request pipeline' do
+          it 'does not re-create a duplicate detached merge request pipeline' do
             expect do
               service.new(@project, @user).execute(@oldrev, @newrev, 'refs/heads/master')
             end.to change { @merge_request.merge_request_pipelines.count }.by(1)
@@ -215,7 +242,7 @@ describe MergeRequests::RefreshService do
             stub_feature_flags(ci_merge_request_pipeline: false)
           end
 
-          it 'does not create a merge request pipeline' do
+          it 'does not create a detached merge request pipeline' do
             expect { subject }
               .not_to change { @merge_request.merge_request_pipelines.count }
           end
@@ -232,7 +259,7 @@ describe MergeRequests::RefreshService do
           }
         end
 
-        it 'does not create a merge request pipeline' do
+        it 'does not create a detached merge request pipeline' do
           expect { subject }
             .not_to change { @merge_request.merge_request_pipelines.count }
         end

spec/support/helpers/stub_worker.rb

+# Inspired by https://github.com/ljkbennett/stub_env/blob/master/lib/stub_env/helpers.rb
+module StubWorker
+  def stub_worker(queue:)
+    Class.new do
+      include Sidekiq::Worker
+      sidekiq_options queue: queue
+    end
+  end
+end