GitLab is a very nice plattform software that provides you a application to host and manage git repositries similar to GitHub, yet it is free and open source and you can install it for your own usage whereever you want.
Recently, we faced a strange error after the machine gitlab runs on had an outage: the previously perfectly working UI to process merge requests on the web ui hung while checking if the merge can be done without further user interaction.
So, in case your gitlab’s merge view hangs on „Checking for ability to automatically merge“ and the hints from the trouble shooting guide do not help:
Check your gitlab-satellite’s working copy if it is inconsistent – in our case, such state blocked the check in the merge view to be completed and rendered the automerge feature of gitlab unusable. If it isn’t, delete it (maybe you also need to remove the tmp/repo_satellites directory) and recreate it with
sudo -u git -H bundle exec rake gitlab:satellites:create RAILS_ENV=production
After that, gitlab was back to normal in our case 
