Automatically add the documentation label via Danger

This makes sure MR are well categorized and Technical Writing people
subscribed to the label will get notifications.
Signed-off-by: Rémy Coutable <remy@rymai.me>

danger/documentation/Dangerfile

 # frozen_string_literal: true
 
+def gitlab_danger
+  @gitlab_danger ||= GitlabDanger.new(helper.gitlab_helper)
+end
+
 docs_paths_to_review = helper.changes_by_category[:docs]
 
-unless docs_paths_to_review.empty?
-  message 'This merge request adds or changes files that require a review ' \
-    'from the Technical Writing team.'
+return if docs_paths_to_review.empty?
+
+message 'This merge request adds or changes files that require a review ' \
+  'from the Technical Writing team.'
+
+return unless gitlab_danger.ci?
 
-  if GitlabDanger.new(helper.gitlab_helper).ci?
-    markdown(<<~MARKDOWN)
-      ## Documentation review
+markdown(<<~MARKDOWN)
+  ## Documentation review
 
-      The following files require a review from a technical writer:
+  The following files require a review from a technical writer:
 
-      * #{docs_paths_to_review.map { |path| "`#{path}`" }.join("\n* ")}
+  * #{docs_paths_to_review.map { |path| "`#{path}`" }.join("\n* ")}
 
-      The review does not need to block merging this merge request. See the:
+  The review does not need to block merging this merge request. See the:
 
-      - [DevOps stages](https://about.gitlab.com/handbook/product/categories/#devops-stages) for the appropriate technical writer for this review.
-      - [Documentation workflows](https://docs.gitlab.com/ee/development/documentation/workflow.html) for information on when to assign a merge request for review.
-    MARKDOWN
+  - [Technical Writers assignments](https://about.gitlab.com/handbook/engineering/technical-writing/#designated-technical-writers) for the appropriate technical writer for this review.
+  - [Documentation workflows](https://docs.gitlab.com/ee/development/documentation/workflow.html) for information on when to assign a merge request for review.
+MARKDOWN
 
-    unless gitlab.mr_labels.include?('documentation')
-      warn 'This merge request is missing the ~documentation label.'
-    end
-  end
+unless gitlab.mr_labels.include?('documentation')
+  gitlab.api.update_merge_request(gitlab.mr_json['project_id'],
+                                  gitlab.mr_json['iid'],
+                                  labels: (gitlab.mr_labels + ['documentation']).join(','))
 end

danger/roulette/Dangerfile

@@ -58,6 +58,8 @@ changes = helper.changes_by_category
 
 # Ignore any files that are known but uncategorized. Prompt for any unknown files
 changes.delete(:none)
+# To reinstate roulette for documentation, remove this line.
+changes.delete(:docs)
 categories = changes.keys - [:unknown]
 
 # Ensure to spin for database reviewer/maintainer when ~database is applied (e.g. to review SQL queries)

lib/gitlab/danger/helper.rb

@@ -102,8 +102,8 @@ module Gitlab
       }.freeze
       # First-match win, so be sure to put more specific regex at the top...
       CATEGORIES = {
-        %r{\Adoc/} => :none, # To reinstate roulette for documentation, set to `:docs`.
-        %r{\A(CONTRIBUTING|LICENSE|MAINTENANCE|PHILOSOPHY|PROCESS|README)(\.md)?\z} => :none, # To reinstate roulette for documentation, set to `:docs`.
+        %r{\Adoc/} => :docs,
+        %r{\A(CONTRIBUTING|LICENSE|MAINTENANCE|PHILOSOPHY|PROCESS|README)(\.md)?\z} => :docs,
 
         %r{\A(ee/)?app/(assets|views)/} => :frontend,
         %r{\A(ee/)?public/} => :frontend,

spec/lib/gitlab/danger/helper_spec.rb

@@ -167,13 +167,13 @@ RSpec.describe Gitlab::Danger::Helper do
 
   describe '#categories_for_file' do
     where(:path, :expected_categories) do
-      'doc/foo'         | [:none]
-      'CONTRIBUTING.md' | [:none]
-      'LICENSE'         | [:none]
-      'MAINTENANCE.md'  | [:none]
-      'PHILOSOPHY.md'   | [:none]
-      'PROCESS.md'      | [:none]
-      'README.md'       | [:none]
+      'doc/foo'         | [:docs]
+      'CONTRIBUTING.md' | [:docs]
+      'LICENSE'         | [:docs]
+      'MAINTENANCE.md'  | [:docs]
+      'PHILOSOPHY.md'   | [:docs]
+      'PROCESS.md'      | [:docs]
+      'README.md'       | [:docs]
 
       'ee/doc/foo'      | [:unknown]
       'ee/README'       | [:unknown]