gitlab-cancel-outdated-pipelines cancels legitimate pipelines

Background

To workaround gitlab limitations, we introduced a new tool to cancel outdated pipelines in ci-package-builder!335 (merged). In a specific case, it cancels a legitimate pipeline.

Reproducibility

1. Create a merge request A proposed-update/blabla against v2025pre (like a package update from Debian).
2. Create a merge request B from v2025pre to v2024-updates, to be ready to land the update in v2024-updates as soon as it landed in v2025pre.
3. Merge A, this will update the branch v2025pre and trigger a pipeline C in branch context to build the package in v2025. At the same time, a pipeline D will be triggered in merge context to update v2024-updates.

The pipeline D will cancel the pipeline C where is should not have been cancelled.

An example is https://gitlab.apertis.org/pkg/apache2/-/jobs/3464371 that wrongly cancelled the pipeline #767227.

Put the ✅ in the most appropriate entry:

1. ✅ always
2. often, but not always
3. rarely

Impact of bug

The new version of the package is not built in v2025pre.

Outcomes

• ci-package-builder!338 (merged)

Management data

This section is for management only, it should be the last one in the description.

/cc @em @Balasubramanian @sudarshan @wlozano

Phabricator link: https://phabricator.apertis.org/T10736