See Start using Git on the command line in our GitLab docs.
GDK provides a local GitLab instance
The GitLab Development Kit (GDK) allows you to test changes locally, on your workstation.
Learn GitLab's UI templates
Three kinds of files handle UI rendering. At its core, GitLab is a Ruby on Rails application. The Ruby on Rails application renders GitLab's front end with
.haml files. HAML (HTML Abstraction Markup Language) is a Ruby-based HTML template system. It's easy to learn and it even closes HTML tags for you!
For Stylesheets, GitLab uses a CSS pre-processor called SASS. SASS (Syntactically Awesome Style Sheets) uses
.scss files that handle all of the usual stuff CSS does, but with a bit more sophistication that helps us keep GitLab's CSS better organized.
Finally, for interactivity and client-side application logic, GitLab uses a framework called Vue.js. It's rare to have to change the
.vue files unless you're changing a Pajamas component, or creating a new one.
Most fixes are a CSS change away
If you can fix it in the browser inspector, you can probably fix it for real in the GitLab codebase. Find small UI issues and submit your changes via merge requests (MRs). Don't worry, you won't break anything, and a reviewer will always help you check your code before it ships.