Feature request: Have the rspec-queue executable output the queue size

[tennety]

Since ci-queue cannot by necessity respect before(:all) hooks, I have a workaround to run the required setup in my CI script. However, I'd like to avoid running it if the queue is empty (i.e. other workers have already exhausted it), so it would be cool to have something like:

unless `rspec-queue --query queue-size`.chomp! == '0'
  # do expensive setup
end

If there's already a straightforward programmatic way to do this, I'm happy to use that instead of adding a feature!