GitLab Merge Request pipeline runs upon a certain number of commits

### Feature Request

Hi,

I have been working the jenkins gitlab source plugin for running multi branch CI pipelines for merge requests. Currently i'm using this configuration for the pipeline:


The pipeline builds for the **current merge request revision** as you can see. I want it to run with the option: **Merging the merge request with the current target branch revision**.
The problem with the latter is that, pipeline builds automatically for every single commit to the target branch of the merge request.

Can a feature be added in such a way that this automatic build for pipeline happens only when there is a specific number of commits to target branch?

If there is an option to specify **the number of commits to target branch** as **100**, then the pipeline for merge request should only **build when it is a 100 commits behind the target branch**.

Thank you.