Fix chance for TestPlanVersion correct updatedAt to be wrong

[howard-e]

There is a chance that should multiple updates be pushed to w3c/aria-at, only the date of the last one will be captured and that will then account for the latest update for any other tests that were updated.

Scenario:

• If w3c/aria-at/tests/alert is updated and pushed to the default branch at 12:03,
• Then w3c/aria-at/tests/checkbox is updated and pushed to the default branch at 12:07,
• Then w3c/aria-at/tests/vertical-temperate-slider is updated and pushed to the default branch at 12:44,
• But the next scheduled update for the imports-test script is at 1:00,
• Then updatedAt date for all 3 newly imported TestPlanVersions will be the-date at 12:44
• 2 of those newly imported TestPlanVersions will be incorrect

That's because the gitCommitDate being used was referencing the latest found git date for entire w3c/aria-at directory at the time of the scheduled script, rather than navigating to each w3c/aria-at/tests/ and checking the most recently recorded time it was updated through git.

[alflennik]

I really appreciate this change, this was a pretty big gotcha with the TestPlanVersions and I'm impressed how small the fix was needed to address it. I ran all the code and verified that importing works. The next time the ARIA-AT team merge multiple PRs at the same time we should take a peek at the shas to verify that they are indeed split out correctly.

[howard-e]

The next time the ARIA-AT team merge multiple PRs at the same time we should take a peek at the shas to verify that they are indeed split out correctly.

Agreed!

[mcking65]

That will be happening a lot after we have the new V2 test format supported (w3c/aria-at#974) because we are going to be rewriting every test plan. So, @howard-e, this is a more important fix than you may have initially realized.