"Merge When Pipeline Succeeds"/"Add To Merge Train When Pipeline Succeeds" displays inconsistent SHAs

Problem

The latest pipeline in this merge request shows that it runs on 5e0f30c3. This is the HEAD sha of refs/merge (a.k.a. combined ref from target and source branches).

On the other hand, system notes shows that "Add To Merge Train When Pipeline Succeeds" was actived for 63320770. This is the HEAD sha of the source branch (in this case reduce-artifact-size). This is misleading and should show 5e0f30c3.

This bug happens on both "Merge When Pipeline Succeeds" and "Add To Merge Train When Pipeline Succeeds".

Proposal

Show the actual SHA of the latest pipeline in system notes.