Backend: `rules:changes` ignores force push event

Summary

I tried to use rules:changes config https://docs.gitlab.com/ee/ci/yaml/index.html#ruleschanges for parent-child pipeline.

This works well, the child pipeline is run on push when something changes in dir folder.

But on force push it is skipped (git push -f). That is kind of a critical issue when e.g. tests should be run to detect issues in changes.

Steps to reproduce

Child:
    stage: s1
    trigger:
        include: dir/.gitlab-ci.yml
        strategy: depend
    rules:
        - changes:
              - dir/*

1. Push something to opened PR so the child pipeline is run and the pipeline is green
2. Break code
3. Commit amend
4. Force push

• the pipeline is still green

What is the current bug behavior?

Pipeline is NOT run on force push

What is the expected correct behavior?

Pipeline is run on force push

Results of GitLab environment info

GitLab Enterprise Edition 14.1.0-ee

Possible fixes

Run child pipelines on force push because it might have changes the contents