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GeezerVison is showing github.com — dev: diff a preview deployment against production by marcleblanc2 · Pull Request #2011 · sourcegraph/docs

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@marcleblanc2

@marcleblanc2 marcleblanc2 commented Sep 18, 2026

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What

Adds dev/diff-deployments.mjs, a script that fetches every page from a Vercel preview deployment and from production (https://sourcegraph.com/docs by default), normalizes the HTML, and reports which pages differ. Documented in AGENTS.md.

node dev/diff-deployments.mjs --site https://<preview>.vercel.app/docs
node dev/diff-deployments.mjs --site <url> --pages /admin,/cli --limit 50 --concurrency 6

How it works

  • Enumerates the union of both sitemaps, plus /robots.txt, /sitemap.xml, /api/versions, /api/releases, and a known-404 page.
  • Strips noise that differs between any two deployments: <script> tags (RSC payload), data-dpl-id, Turbopack chunk hashes, the Cloudflare cdn-cgi anchor, sitemap <lastmod>. Sitemap <url> blocks are sorted.
  • Strips the /docs basePath only when the two sites serve under different basePaths; when both serve under /docs, a missing prefix is a real bug and is reported.
  • Node builtins + OS diff -u; no new dependencies.
  • Prints a summary; writes the combined unified diff to logs/diff-deployments-<timestamp>.diff when pages differ. Exits 1 on any difference or fetch failure.

Worked example

Run against the preview for #1997 (rebased on main + #1977): 504 identical, 3 differ, 0 failed. All three differences come from #1977's root-relative <img> fix (/sourcegraph-mark.svg → /docs/sourcegraph-mark.svg on /integration/browser-extension and /self-hosted/deploy; /aws-ami-marketplace.png → /docs/aws-ami-marketplace.png on /self-hosted/deploy/machine-images/aws-ami). The root-relative paths 404 on prod today and the /docs/ ones return 200, so those are fixes. #1997's own commits change nothing in rendered HTML.

An earlier run against the pre-rebase preview flagged 501 pages, all explained by the branch lacking #2001 (per-page canonical) and #1975 (lazy-load images), which confirms the normalizer does not hide <head> or attribute changes.

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@marcleblanc2 @ampagent
dev: diff a preview deployment against production
de0d012 
Fetches every sitemap page from both sites, strips build ids, chunk hashes,
the RSC payload and (when they differ) the basePath, and writes a unified
diff of the pages that still differ to logs/.

Amp-Thread-ID: https://ampcode.com/threads/T-01a0b2e2-a101-7132-b956-da8493ee40b5
Co-authored-by: Amp <[email protected]>
@vercel

vercel Bot commented Sep 18, 2026

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The latest updates on your projects. Learn more about Vercel for GitHub.

Project Deployment Actions Updated
sourcegraph-docs Ready Ready Preview Sep 18, 2026 5:21am UTC

Request Review
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@github-actions

github-actions Bot commented Sep 18, 2026

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Open the Diff Tour for this PR in Sourcegraph
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@github-actions

github-actions Bot commented Sep 18, 2026

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⚠️ Spell check found 1 issue(s) in this PR

Only findings on lines added by this PR, and in its title and description, are shown.

Pull request description

  • line 13, column 171
    • lastmod → lsmod

Please correct the spelling, or add words which are correct to cspell-allow-list.txt.

Run npx cspell@10 --no-progress --dot '**/*' locally to check the full repository.
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This branch was successfully deployed

1 active deployment
Preview — de0d0125 Deployed Sep 18, 2026 by vercel[bot]
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@marcleblanc2
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