Your team's GitLab CE pipeline runs a validation job for network automation code. Developers report that every time they push to a branch that has an open merge request, TWO pipelines start: one branch pipeline and one merge request pipeline. This wastes CML runner capacity and doubles the CML topology spin-up cost. You need to ensure only the merge request pipeline runs when an MR is open, while still allowing branch pipelines on branches without any open MR. Which top-level configuration accomplishes this?