1 files changed, 52 insertions, 5 deletions
diff --git a/lib/gitlab/danger/changelog.rb b/lib/gitlab/danger/changelog.rb
index 4427c331b8e..607ca1200a0 100644
--- a/lib/gitlab/danger/changelog.rb
+++ b/lib/gitlab/danger/changelog.rb
@@ -11,8 +11,36 @@ module Gitlab
         'meta'
       ].freeze
       NO_CHANGELOG_CATEGORIES = %i[docs none].freeze
+      CREATE_CHANGELOG_COMMAND = 'bin/changelog -m %<mr_iid>s "%<mr_title>s"'
+      CREATE_EE_CHANGELOG_COMMAND = 'bin/changelog --ee -m %<mr_iid>s "%<mr_title>s"'
+      CHANGELOG_MODIFIED_URL_TEXT = "**CHANGELOG.md was edited.** Please remove the additions and create a CHANGELOG entry.\n\n"
+      CHANGELOG_MISSING_URL_TEXT = "**[CHANGELOG missing](https://docs.gitlab.com/ee/development/changelog.html)**:\n\n"
 
-      def needed?
+      OPTIONAL_CHANGELOG_MESSAGE = <<~MSG
+      If you want to create a changelog entry for GitLab FOSS, run the following:
+
+          #{CREATE_CHANGELOG_COMMAND}
+
+      If you want to create a changelog entry for GitLab EE, run the following instead:
+
+          #{CREATE_EE_CHANGELOG_COMMAND}
+
+      If this merge request [doesn't need a CHANGELOG entry](https://docs.gitlab.com/ee/development/changelog.html#what-warrants-a-changelog-entry), feel free to ignore this message.
+      MSG
+
+      REQUIRED_CHANGELOG_MESSAGE = <<~MSG
+      To create a changelog entry, run the following:
+
+          #{CREATE_CHANGELOG_COMMAND}
+
+      This merge request requires a changelog entry because it [introduces a database migration](https://docs.gitlab.com/ee/development/changelog.html#what-warrants-a-changelog-entry).
+      MSG
+
+      def required?
+        git.added_files.any? { |path| path =~ %r{\Adb/(migrate|post_migrate)/} }
+      end
+
+      def optional?
         categories_need_changelog? && without_no_changelog_label?
       end
 
@@ -20,16 +48,35 @@ module Gitlab
         @found ||= git.added_files.find { |path| path =~ %r{\A(ee/)?(changelogs/unreleased)(-ee)?/} }
       end
 
-      def sanitized_mr_title
-        gitlab.mr_json["title"].gsub(/^WIP: */, '').gsub(/`/, '\\\`')
-      end
-
       def ee_changelog?
         found.start_with?('ee/')
       end
 
+      def modified_text
+        CHANGELOG_MODIFIED_URL_TEXT +
+          format(OPTIONAL_CHANGELOG_MESSAGE, mr_iid: mr_iid, mr_title: sanitized_mr_title)
+      end
+
+      def required_text
+        CHANGELOG_MISSING_URL_TEXT +
+          format(REQUIRED_CHANGELOG_MESSAGE, mr_iid: mr_iid, mr_title: sanitized_mr_title)
+      end
+
+      def optional_text
+        CHANGELOG_MISSING_URL_TEXT +
+          format(OPTIONAL_CHANGELOG_MESSAGE, mr_iid: mr_iid, mr_title: sanitized_mr_title)
+      end
+
       private
 
+      def mr_iid
+        gitlab.mr_json["iid"]
+      end
+
+      def sanitized_mr_title
+        helper.sanitize_mr_title(gitlab.mr_json["title"])
+      end
+
       def categories_need_changelog?
         (helper.changes_by_category.keys - NO_CHANGELOG_CATEGORIES).any?
       end