[nedtwigg]

Once a change is approved, later batches compare against it, so it stops showing as a change. A merged PR's commit, a later commit on the PR, and a re-render at the same commit all open on "Nothing differs", with no link to what happened. For example, #60's merge commit reads as 124 unchanged. The diffs only survive on the batch the approval was made on, and nothing leads there.

What it does

• Finds the base: a batch's base is the newest finished batch of the default branch at a commit it reaches, other than its own commit. It needs no schema change, no Git in the Worker, and no parent order, so it also works on batches already recorded.
• Lists what's been approved since then: a story is listed if it doesn't differ now but would differ by the base's approvals. It's shown between what it replaced and this image, including approved additions and removals.
• Shows it on the batch page: a banner says "124 stories changed and approved earlier", with a "See what changed" button. There's also a count and a new "Approved earlier" option under Show.
• Offers no chat either: chat answers 404 for a story its batch reads as unchanged, so its panel is hidden on these rows.
• Offers no decision: each story opens with its usual before, after and diff, plus a link to the batch it was approved on. There are no approve or reject buttons, and pressing a says why. The server already refused such a decision as stale-decision.
• Stores new diffs on push: /diffs/needed now includes these pairs, because a branch that approved several times creates a before-and-after pair that no single commit compared.

Later batches on the default branch use the merge as their base, so a merge shows only what it brought, and the commits after it show nothing.

Testing

• pnpm test passes after merging main: ui 105, store 632 (92 skipped), render 148, cli 516. The last commit, which hides chat on these rows, had a typecheck and the filter and delta tests only.
• New tests cover the rule, the SQL on a store (merge, later branch commit, next default-branch commit, re-render), real Git through approvedSinceOf, the route including the refused decision, and the stored diff on push.
• Dogfooded through selfie ui on a scratch repo that merges the real header change (before and after Storybooks from 9fb57fd and 6e330ef):
  • The merge batch reads 124 unchanged, and the new list shows all 124 with real diffs, such as 21,057 pixels on pages-batch--dark.
  • The batch the approval was made on lists nothing, since it still shows those as changed itself.
• The three new stories render, and one asserts that there are no decision buttons.

Before you rely on it

• Not tried on the hosted Worker: it needs a deploy, which I haven't done. The hosted route shares its store code with the tests above, but the page itself has only run locally.
• Some older diffs may be missing on the hosted site: diffs are stored by pair, and only new pushes store these extra pairs. A story whose pair was never compared should show its before and after images with "The pixels couldn't be compared" instead of a diff. That's from reading the code, not from seeing it happen. A single-approval PR like Link the demo videos from the README, and say what's really built #60 already has its pair.

Known limitations

• Re-rendering an old commit on the default branch: that batch can become the newest, so the list reaches further back and shows more than it needs to.
• Read once per page load: the list doesn't refresh when the window regains focus, unlike the rest of the batch. Approvals made elsewhere appear on the next load.
• Every batch page pays for it: the banner needs the count, so each load makes one more request. On the Worker that's two more D1 reads, plus a read of each approving batch's Storybook and viewports.
• Only reached through the filter: a story page opened without ?show=approved-earlier still just says "Unchanged".

Not in this PR

GitHub statuses on later commits still go stale: 05a0588 says "124 changed, waiting for approval" although its batch reads 124 unchanged, because publish only updates the commit that was decided on.

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