Add commit check for "Fixes #issue" in comment

[lifflander]

What Needs to be Done?

If a PR is created, users should normally annotate that PR as it fixes an issue so the issue automatically closes when the PR is merged. However, it's easy to forgot to add that to the comment.

Write a PR hook (like the issue style checks) that greps for that in the issue comment so we can inform the user if they forgot.

You can probably model it after the commit check hook, that I've developed in this repo: https://github.com/DARMA-tasking/check-commit-format

[PhilMiller]

Is the PR description available to the hooks? The relevant line won't necessarily appear in a commit message

[lifflander]

Yes, the PR description is available to the workflow. Note that issues and PRs are the same structure in GitHub, just a bit set to indicate which one. The code to get to it in a workflow will look something like:

contains(${{ github.event.issue.body}}, 'Fixes')