ci(lint): add shell linter - Differential ShellCheck

[jamacku]

Differential ShellCheck is a GitHub action that performs differential ShellCheck scans on shell scripts changed via PR and reports results directly in PR.

I see that your script is in great shape, but I think that you might find the differential-shellcheck action useful. It is able to produce reports in SARIF format. GitHub understands this format and is able to display it nicely as a PR comment, and on the Files Changed tab, please see below.

Documentation is available at @redhat-plumbers-in-action/differential-shellcheck. Let me know If you are missing some feature or option. I'm always happy to extend functionality.

[andyfeller]

@jamacku : thank you for offering an idea to improve our workflow CI process! ❤️

In the past, I have used ludeeus/action-shellcheck for personal shell-based GitHub CLI extensions I built and maintain. That said, I can see why a project might adopt Differential ShellCheck:

"needed some way to verify incoming Pull Requests without getting warnings and errors about already merged and for years working code."

Putting aside whether all errors should be identified and fixed, we don't have a linting process for the repository, which is largely powered by a shell script, I think this is something that would benefit the workflows here given several key features below:

• Basic shell scripting linting / testing via koalaman/shellcheck
• SARIF support - warnings are visible in the Changed files tab of the Pull-Request and as comment alerts on Pull-Requests
• Results displayed as Job Summaries - example

@williammartin : Any concerns or thoughts about how we might adopt this?

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.