Bitbucket PR importer fails if all changesets already known
Import failed for PR iid 460, error Could not log head of topic bitbucket-pr-460, trace: /opt/gitlab/embedded/service/gitlab-rails/lib/gitlab/git/repository.rb:1001:in `pull_force_topic'
In that case, I checked, pull_force_topic
indeed had an empty pull. Whatever the reason, it should be easy to recover from that one, provided we return a clear indication that it's been empty.