Add auto-cancellation workflow

[aaemnnosttv]

Summary

Addresses issue #2027

Relevant technical choices

• Used dedicated workflow for cancelling all relevant workflows rather than updating individual flows and allows for cancelling a workflow before it runs

Testing

• Triggered workflow, cancelled by subsequent commit
• Cancel workflow run

Screenshots

Checklist

• My code is tested and passes existing unit tests.
• My code has an appropriate set of unit tests which all pass.
• My code is backward-compatible with WordPress 4.7 and PHP 5.6.
• My code follows the WordPress coding standards.
• My code has proper inline documentation.
• I have added a QA Brief on the issue linked above.
• I have signed the Contributor License Agreement (see https://cla.developers.google.com/).

[felixarntz]

@aaemnnosttv One comment here, but nothing blocking.

[felixarntz]

According to the docs, this also supports workflow names - wouldn't this be more intuitive to use?

[aaemnnosttv]

Looking at it again, that would be okay too. I originally read the docs for that to mean you could use the actual workflow name which I wouldn't want but it's the file name which is much more stable.

I guess it depends on how GH treats the workflow ID in relation to the file name. I would expect the ID to remain unchanged even if the workflow changed completely.

After taking a closer look at this, I found the API documentation for listing workflow runs which is what this uses (via octokit).

List all workflow runs for a workflow. You can also replace :workflow_id with :workflow_file_name. For example, you could use main.yml. You can use parameters to narrow the list of results. For more information about using parameters, see Parameters.

So that means we wouldn't need to use the full .github/workflows/zips.yml path which is what I was thinking it would require.

File names it is then? 😄

[aaemnnosttv]

Updated to use filenames instead. It's much cleaner and doesn't require referencing something external to update. Also, the ability to use a filename instead is a feature provided by the underlying GitHub API (example) rather than the extension so this is much better I think 👍