Ci/change pr check links target branch

[f-hollow]

Description

The pr-check-links has a notion of a base-commit. This is a commit at which the feature branch was forked. This commit is determined using the git merge-base command. After that, the changes in all subsequent commits are checked by pr-check-links.

On numerous occasions (the latest one is #356 and the related job), the contributors rebased their feature branch directly against upstream while their fork origin/main branch stayed outdated. Due to this, the base commit was determined incorrectly, which resulted in checking links unrelated to the changes in the pull request.

This PR changes the branch against which the base commit is determined from hard-coded origin/main to the branch defined by the CI environment variables TARGET_REPO_URL and TARGET_BRANCH. These variables are set to the upstream/main branch.

Related

• Lechee check on PR is checking whole portal, instead of just modified content #101

Testing

Testing was done in this testing environment.

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[github-actions]

🎉 A preview for this PR is available at: https://preview-developer.espressif.com/pr366/

[github-actions]

🎉 A preview for this PR is available at: https://preview-developer.espressif.com/pr366/

[github-actions]

🎉 A preview for this PR is available at: https://preview-developer.espressif.com/pr366/