ci[pr-check-links]: dump links from baseline commit for pr link checking

[f-hollow]

Description

More recent updates in main

In the check_links_in_diffs workflow, the feature branch links are compared to the main branch links. As finalizing changes in a feature branch might take a while, its links get outdated compared to main. This can lead to false positives.

In the proposed updates, the feature branch links are compared to the main branch commit at which the feature branch was created. In this way, the more recent changes in main do not affect link checking.

Anchors / fragments affected by updates

All links are dumped into .lycheeignore from the main branch commit at which the feature branch was created. File names or headings to which the anchor / fragment point might get updated. Yet, checking of fragment links is bypassed. This PR adds steps to identify the files with updated file names and heading titles and removes all links in these files from .lycheeignore.

The downside is that if somebody alters a filename of a heading title, all anchor links in this file will be checked anew. On the other hand, if somebody touches an existing file, that would most likely be a maintainer or the author who be in the position to make sure that all links in these files are valid.

Cleaning up artifacts and any changes to files done in CI

Also, there were a couple of occasions when the check still failed after corrections were pushed. Creating a new PR with these changes had all checks passed successfully. A culprit might have been a cached file with old links that were not overridden (no other ideas for now). A step has been added to clean up all changes done in CI after the check completes.

Related

This updates the changes introduced in PR #107. The changes are tracked is issue #101.

Testing

Tests run:

• Ensure the workflow does not check main in more recent commits compared to baseline commit
  • Injecting an invalid link in main in a more recent commit should not affect pr-check-links
• Ensure that invalid links before the baseline commmit on main do not affect pr-check-links
  • Injecting an invalid link in main in the baseline commit should not affect pr-check-links
• Ensure that anchors/fragments in a file pointing to heading titles of a file removed or modified in a PR get identified
  • Anchor/fragment links pointing to removed or modified files should not be present in .lycheeignore
• Ensure that anchors/fragments in a file pointing to heading titles of a file renamed in a PR get identified
  • Anchor/fragment links pointing to renamed files should not be present in .lycheeignore

---

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.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[pedrominatel]

LGTM

[f-hollow]

@horw PTAL