Pipeline triggering works for maximum 2000 branches

Summary

When a repository has ~2000+ branches then pipelines will only auto-trigger for the oldest 2000.

In my case the repository is mirrored from GitHub and cleaning up old branches is a manual process so stale branches build up.

Steps to reproduce

Create a repository with over 2000 branches and push commits to the latest branches.

Example Project

I have now deleted many of the branches on my repository

What is the current bug behavior?

New branches do not trigger pipelines when commits are pushed.

What is the expected correct behavior?

Pipelines should be triggered for all branches.

Relevant logs and/or screenshots

None

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

N/A

Results of GitLab application Check

N/A

Possible fixes

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