Merge branch 'nfriend-ignore-rubocop-cache-files' into 'master'

Ignore files in tmp/rubocop_cache/**

See merge request gitlab-org/gitlab-ce!28672

.gitignore

@@ -79,3 +79,4 @@ package-lock.json
 /junit_*.xml
 /coverage-frontend/
 jsdoc/
+**/tmp/rubocop_cache/**
\ No newline at end of file