Query: Preserve query strings in old slug redirects.

[deepakpra]

Why?

wp_old_slug_redirect() redirects requests for previous post slugs to the current permalink, but it currently drops the original query string.

This can remove tracking or campaign parameters. For example, /old-slug/?utm_source=flyer redirects to /new-slug/ instead of /new-slug/?utm_source=flyer.

How?

This preserves the original $_SERVER['QUERY_STRING'] when building the old-slug redirect URL.

The query string is appended as-is, without parsing or rebuilding it, so encoded values and duplicate query args remain unchanged.

Testing

Automated test:

npm run test:php -- --filter Tests_Rewrite_OldSlugRedirect

Manual test:

1. Create or edit a published post with the slug old-slug.
2. Change the post slug to new-slug.
3. Visit /old-slug/?utm_source=flyer&campaign=spring.
4. Confirm it redirects to /new-slug/?utm_source=flyer&campaign=spring

Trac ticket: #65267

[github-actions]

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Props deepakprajapati, westonruter.

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[github-actions]

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