How to reconfigure the external URL of a GitLab server
In some cases you might encounter the problem of having to reconfigure, the external URL address of an already working GitLab server. At the first sight that might look daunting, especially when important repos are involved and people are depending on this installation. However the solution is rather simple. Login to your GitLab server and locate the following file /etc/gitlab/gitlab.rb. Search for the setting external_url and set the new desired value e.g:
Save the changes, and then reconfigure and restart the GitLab instance in order to apply the changes.