workflow: find merge conflicts

[yaauie]

Release notes

[rn:skip]

What does this PR do?

since mergify creates commits with merge conflicts, having a check that calls out the conflict can be helpful in cases where the conflict doesn't otherwise break the build.

Why is it important/What is the impact to the user?

No user impact.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works

[mergify]

This pull request does not have a backport label. Could you fix it @yaauie? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• backport-8.x is the label to automatically backport to the 8.x branch.
• If no backport is necessary, please add the backport-skip label

[donoghuc]

This is a very good off the shelf action ❤️

[v1v]

Let's pin the version when using third-party actions. See

Suggested change

	uses: olivernybroe/action-conflict-finder@v4.0
	uses: olivernybroe/action-conflict-finder@1a949ebd954a9eaee58802229ea5f9c69fb93a50 v4.1

OTOH, we don't recommend to use GH actions that are not actually maintained for a while, in this case I've just seen 4.1 has been shipped yesterday. But, we might need to be cautious as there was recently some interesting supply chain attack to one GH action, see https://semgrep.dev/blog/2025/popular-github-action-tj-actionschanged-files-is-compromised/.

If it helps, we have enabled the pre-commit for detecting those merge conflicts in the source code in some other repositories. See https://github.com/elastic/beats/blob/main/.pre-commit-config.yaml and https://github.com/elastic/beats/blob/main/.github/workflows/pre-commit.yml.

I don't know if that's what we think it can be useful, but it can help to provide a common tool for local development and CI. What do you think?