GitLab has a great issue tracker but you can also use an external one such as Jira, Redmine, YouTrack, or Bugzilla. External issue trackers are configurable per GitLab project.
Once configured, you can reference external issues using the format
CODEis a unique code for the tracker.
123is the issue number in the tracker.
These references in GitLab merge requests, commits, or comments are automatically converted to links to the issues.
You can keep GitLab’s issue tracker enabled in parallel or disable it. When enabled, the Issues link in the GitLab menu always opens the internal issue tracker. When disabled, the link is not visible in the menu.
The configuration is done via a project’s Services.
To enable an external issue tracker you must configure the appropriate Service. Visit the links below for details:
To save you the hassle from configuring each project’s service individually, GitLab provides the ability to set Service Templates which can then be overridden in each project’s settings.
Read more on Services Templates.