make removed URL check aware of docs/redirects.txt

[rajannpatel]

Description

This PR updates the check-removed-urls.yml GitHub workflow to prevent false positives when a documentation page is intentionally removed or renamed, but a proper redirect has already been configured in docs/redirects.txt.

Previously, the workflow performed a strict text diff on the built HTML output. If a URL disappeared, the check failed immediately, completely unaware that a redirect existed.

Key Changes

• Added workflow_call Inputs: decoupled the base reference variables so this workflow can be cleanly reused by other pipelines.
• Path Normalization: Streamlined the find and sed pipeline to parse built HTML structures safely and output clean, predictable path formats.
• Redirect-Aware Validation: Replaced the Bash loop with an inline Python verification script. It parses docs/redirects.txt using the native csv module and checks all structural markdown possibilities (page.md, page/index.md, or directory-level paths) before flagging a URL as missing.

Testing Instructions

1. If a PR removes a page without adding it to docs/redirects.txt, the workflow should fail and list the unhandled URL.
2. If a PR removes a page and correctly logs the source path in docs/redirects.txt, the workflow should print a green checkmark (✅ Ignored) and pass successfully.

Checklist

• Tested changes against private/public fork contexts
• Handled empty lines and comment blocks inside redirects.txt
• Validated fallback behavior for reusable workflow triggers
• Have you updated CHANGELOG.md with relevant non-documentation file changes?
• Have you updated the documentation for this change?

[medubelko]

@SecondSkoll I think you were the principal author behind this script, so I'd like to defer this one to you.

[SecondSkoll]

Checked and validated against my own docs, works just fine.

Note: The old check was broken by the introduction of rerediraffe.

[medubelko]

@jahn-junior While this might not fit our ultimate goals for rerediraffe, this fixes a broken workflow. If the script were moved to an external file, would that be a satisfactory stop-gap?

[jahn-junior]

@medubelko

@jahn-junior While this might not fit our ultimate goals for rerediraffe, this fixes a broken workflow. If the script were moved to an external file, would that be a satisfactory stop-gap?

No complaints from me. I haven't had time to look at the Python in detail, but it seems simple enough.

[SecondSkoll]

Could you please move the Python script in the "Compare URLs" step to /docs/_dev/, and then then call it in the workflow?

[rajannpatel]

Could you please move the Python script in the "Compare URLs" step to /docs/_dev/, and then then call it in the workflow?

@SecondSkoll please let me know what you think?

Changes made

[SecondSkoll]

LGTM, @jahn-junior any final notes or are you happy to merge this in now?

[jahn-junior]

I'm happy with the overall shape of this. Just one question about the args in the Python script. Once we've settled that, I'll go ahead and merge.

[jahn-junior]

Suggested change

	* `.github/workflows/check-removed-urls.yml` [#PR_NUMBER](https://github.com/canonical/sphinx-stack/pull/#PR_NUMBER)
	* `.github/workflows/check-removed-urls.yml` [#612](https://github.com/canonical/sphinx-stack/pull/612)

Leaving this comment so we don't forget to replace these before merge.