Auto merge of #14450 - SijmenSchoon:master, r=Wafflespeanut

Implement tidy commit message test

<!-- Please describe your changes on the following line: -->
Makes tidy check commit messages since the latest merge, failing if one of them contains the string "WIP".

I have written a test for my changes, although it is a bit hacky.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #14388.

<!-- Either: -->
- [x] These changes do not require tests because this would require playing with a new/existing git repo

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/14450)
<!-- Reviewable:end -->

0 files changed, 0 insertions, 0 deletions