Automatic merge of gitlab-org/gitlab-ce master

changelogs/unreleased/66616-follow-up-documentation-for-merge-trains-cancel-when-running.yml

+---
+title: Update merge train documentation
+merge_request: 32218
+author:
+type: changed

changelogs/unreleased/use_default_external_auth_label_empty.yml

+---
+title: Prevent empty external authorization classification labels from overriding
+  the default label
+merge_request: 32517
+author: Will Chandler
+type: fixed

doc/ci/merge_request_pipelines/pipelines_for_merged_results/index.md

@@ -61,6 +61,20 @@ CAUTION: **Warning:**
 Make sure your `gitlab-ci.yml` file is [configured properly for pipelines for merge requests](../index.md#configuring-pipelines-for-merge-requests),
 otherwise pipelines for merged results won't run and your merge requests will be stuck in an unresolved state.
 
+## Automatic pipeline cancelation
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/issues/12996) in [GitLab Premium](https://about.gitlab.com/pricing/) 12.3.
+
+GitLab CI can detect the presence of redundant pipelines,
+and will cancel them automatically in order to conserve CI resources.
+
+When a user merges a merge request immediately within an ongoing merge
+train, the train will be reconstructed, as it will recreate the expected
+post-merge commit and pipeline. In this case, the merge train may already
+have pipelines running against the previous expected post-merge commit.
+These pipelines are considered redundant and will be automatically
+canceled.
+
 ## Troubleshooting
 
 ### Pipelines for merged results not created even with new change pushed to merge request

lib/gitlab/import_export/project_tree_restorer.rb

@@ -107,7 +107,7 @@ module Gitlab
 
       def project_params
         @project_params ||= begin
-          attrs = json_params.merge(override_params).merge(visibility_level)
+          attrs = json_params.merge(override_params).merge(visibility_level, external_label)
 
           # Cleaning all imported and overridden params
           Gitlab::ImportExport::AttributeCleaner.clean(relation_hash: attrs,
@@ -135,6 +135,13 @@ module Gitlab
         { 'visibility_level' => level }
       end
 
+      def external_label
+        label = override_params['external_authorization_classification_label'].presence ||
+          json_params['external_authorization_classification_label'].presence
+
+        { 'external_authorization_classification_label' => label }
+      end
+
       # Given a relation hash containing one or more models and its relationships,
       # loops through each model and each object from a model type and
       # and assigns its correspondent attributes hash from +tree_hash+

spec/lib/gitlab/import_export/project_tree_restorer_spec.rb

@@ -512,6 +512,24 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
         expect(Milestone.find_by_title('Group-level milestone').iid).to eq(2)
       end
     end
+
+    context 'with external authorization classification labels' do
+      it 'converts empty external classification authorization labels to nil' do
+        project.create_import_data(data: { override_params: { external_authorization_classification_label: "" } })
+
+        restored_project_json
+
+        expect(project.external_authorization_classification_label).to be_nil
+      end
+
+      it 'preserves valid external classification authorization labels' do
+        project.create_import_data(data: { override_params: { external_authorization_classification_label: "foobar" } })
+
+        restored_project_json
+
+        expect(project.external_authorization_classification_label).to eq("foobar")
+      end
+    end
   end
 
   describe '#restored_project' do