Support merge_group event natively

[masaru-iritani]

What

Support merge_group event natively.

Why

Closes #432

Our team uses the merge queue to serialize and validate changes on the default branch. I want to run ShellCheck when a change is added to the merge queue so that I can detect problems introduced by a bad merge before pushing them to the default branch.

While I can configure the workflow to use "manual" triggering event with the base & head SHAs, it'd be convenient if the workflow natively support merge_group.

How tested

Will see the CI test results.

References

The definition of merge_group event.
https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#merge_group

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.89%. Comparing base (b8c7b83) to head (f753aef).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #433      +/-   ##
==========================================
+ Coverage   85.71%   85.89%   +0.17%     
==========================================
  Files           5        5              
  Lines         315      319       +4     
==========================================
+ Hits          270      274       +4     
  Misses         45       45              

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[jamacku]

Thank you for contributing. At first glance, it seems great.

Please remove the Merge commit from the history.

[masaru-iritani]

Please remove the Merge commit from the history.

Sure, I did.

[jamacku]

I have enabled the merge queue for the main branch. Can you also provide a workflow to run Differential ShellCheck in the merge queue? It would be very helpful. Thank you.

[masaru-iritani]

Thank you for enabling the merge queue, @jamacku!

I created another pull request #434 to illustrate how to run Differential ShellCheck on a merge_group event without this change.

[jamacku]

Thank you for enabling running ShellCheck on merge_group. Unfortunately, it seems that we hit an issue where if the branch doesn't contain any previous commits the base is referred to as sha 0000000000000000000000000000000000000000.

I think that the github.event.merge_group.base_sha is holding the same value.

[jamacku]

The code looks great. LGTM

Thank you for your contribution. I'm going to merge this PR. Only this repository uses @main, so unless we release a new version, nobody will be able to use this feature.

I plan to do some testing, and I'll try to find a way how to fix the issue mentioned in #433 (comment)

[masaru-iritani]

Thank you for incorporating this change and working on some tests!

if the branch doesn't contain any previous commits the base is referred to as sha 0000000000000000000000000000000000000000.

Ah, I didn't thought about the case. Although I believe in most cases the workflow will be enabled for merge_group after using the merge queue at least once, the workflow may need to handle the case by making the check non-differential.

[jamacku]

So, I have verified that merge_group works as expected:

• https://github.com/redhat-plumbers-in-action/differential-shellcheck/actions/runs/10181482097/job/28161747618#step:5:1

The issue with 000... is appearing on push (triggering-event: push) to merge queue temporary branch:

• https://github.com/redhat-plumbers-in-action/differential-shellcheck/actions/runs/10181482013/job/28161747328#step:5:928

For a workaround, you could provide a list of branches, etc. (e.g. on: push ; branches: [ main ]), or you can have the merge_group trigger in a separate workflow.