Step 1. Fetch and check out the branch for this merge request

git fetch https://gitlab.gnome.org/sebastien/gtk.git master
git checkout -b sebastien/gtk-master FETCH_HEAD

Step 2. Review the changes locally

Step 3. Merge the branch and fix any conflicts that come up

git fetch origin
git checkout origin/master
git merge --no-ff sebastien/gtk-master

Step 4. Push the result of the merge to GitLab

git push origin master

Note that pushing to GitLab requires write access to this repository.

Tip: You can also checkout merge requests locally by following these guidelines.