Disable changelog check on docs-only MRs

danger/changelog/Dangerfile

@@ -29,6 +29,10 @@ def ce_port_changelog?(changelog_path)
   helper.ee? && !ee_changelog?(changelog_path)
 end
 
+def docs_only_change?
+  helper.changes_by_category.keys == [:docs]
+end
+
 def check_changelog(path)
   yaml = YAML.safe_load(File.read(path))
 
@@ -55,7 +59,7 @@ def sanitized_mr_title
   gitlab.mr_json["title"].gsub(/^WIP: */, '').gsub(/`/, '\\\`')
 end
 
-changelog_needed = (gitlab.mr_labels & NO_CHANGELOG_LABELS).empty?
+changelog_needed = !docs_only_change? && (gitlab.mr_labels & NO_CHANGELOG_LABELS).empty?
 changelog_found = git.added_files.find { |path| path =~ %r{\A(ee/)?(changelogs/unreleased)(-ee)?/} }
 
 if git.modified_files.include?("CHANGELOG.md")