GitLab RT is a Ruby + Rack implementation of a simple daemon to communicate with RT about new commits.
Currently, it only will update the "Referred to by" link of a ticket to point back to any commits that reference that ticket.
To install for deployment, be sure to have the bundler gem installed, and then you can do:
RUBY=/path/to/ruby
$RUBY/bin/bundle install --deployment --binstubs --shebang $RUBY/bin/ruby
You will also need to create a config.rb file for your environment. There is an example provided.