The GitLab Files integration allows you to take a link to a GitLab file or a permalink to lines of code and display them into code blocks in GitBook.
How it works
After installing the GitLab Files integration, you're able to insert it into a GitBook file in the (CMD + /) menu.
Insert the integration, paste your link, and the integration will display the code in a formatted code block.
In order to view code from private repositories, you'll need to authorize with your GitLab Account in the integration's configuration page.