ci: add changelog verification workflow

[vanshika622]

Fixes #2315

Changes

• Add the workflow to verify the changes in changelog.md

Please provide a brief description of the changes here.

For non-trivial changes, follow the change proposal process.

• Related issues #
• Related OTEP(s) #
• Links to the prototypes (when adding or changing features)
• CHANGELOG.md file updated for non-trivial changes
• Spec compliance matrix updated if necessary

[Copilot]

Pull request overview

This PR adds a GitHub Actions workflow to enforce CHANGELOG.md updates for pull requests, addressing issue #2315. The workflow automatically verifies that non-trivial changes include corresponding CHANGELOG.md updates.

Key changes:

• New CI workflow that checks for CHANGELOG.md modifications in PRs
• Support for bypass labels ("Skip Changelog" and "dependencies") to exclude certain PRs
• Validation logic that allows CHANGELOG-only PRs and fails PRs with code changes but no CHANGELOG update

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[pellared]

The new workflow does not seem to work correctly. Why not doing the same as in https://github.com/open-telemetry/opentelemetry-go/blob/main/.github/workflows/changelog.yml?

[vanshika622]

The new workflow does not seem to work correctly. Why not doing the same as in https://github.com/open-telemetry/opentelemetry-go/blob/main/.github/workflows/changelog.yml?

I implemented a custom logic to handle the changelog checks, but I agree that it’s better to follow the same conventions used across the other OpenTelemetry repositories. I will update the workflow

[pellared]

yamllint is failing https://github.com/open-telemetry/opentelemetry-specification/actions/runs/20038553862/job/57466822059?pr=4776

[vanshika622]

yamllint is failing https://github.com/open-telemetry/opentelemetry-specification/actions/runs/20038553862/job/57466822059?pr=4776

yes working on the same and some makrdown one also failing

[pellared]

Tested. Works as expected.

[carlosalberto]

Let's wait for @arminru to review, and let's advertise this in our Spec call.

[trask]

this fixes a subtle bug in the workflow, which is that once a new commit is merged to main (which updates the CHANGELOG.md), the diff with ${{ github.base_ref }} will think the CHANGELOG.md has been updated (this is what using --merge-base fixes)

(also I inlined FETCH_HEAD since the extra fetch isn't needed due to using fetch-depth: 0 above)

Suggested change

	echo "Fetching base branch..."
	git fetch origin ${{ github.base_ref }} --depth=1
	echo "Checking for CHANGELOG modifications..."
	if git diff --name-only FETCH_HEAD | grep -q 'CHANGELOG'; then
	echo "Checking for CHANGELOG modifications..."
	if git diff --name-only --merge-base origin/${{ github.base_ref }} | grep -q 'CHANGELOG'; then