Error changelog script if wrong dev server

app/features/changelog/core/entries.server.ts

@@ -55,6 +55,16 @@ export function allEntries(): ChangelogGraphicEntry[] {
 		.map(parseEntryFile);
 }
 
+/**
+ * Sha of the commit the entries are read from, letting a caller check it is
+ * talking to a server running the same checkout it is.
+ */
+export function headSha(): string {
+	return execFileSync("git", ["rev-parse", "HEAD"], {
+		encoding: "utf8",
+	}).trim();
+}
+
 function parseEntryFile(fileName: string): ChangelogGraphicEntry {
 	const rawMarkdown = fs.readFileSync(
 		path.join(RESOLVED_CHANGELOG_DIR, fileName),

app/features/changelog/loaders/changelog-image.server.ts

@@ -6,6 +6,7 @@ export const loader = ({ request }: LoaderFunctionArgs) => {
 	const { since } = changelogSearchParams.parse(request);
 
 	return {
+		headSha: Entries.headSha(),
 		entries: since ? Entries.entriesSince(since) : Entries.allEntries(),
 	};
 };

app/features/changelog/routes/changelog-image.tsx

@@ -20,7 +20,10 @@ export default function ChangelogImagePage() {
 					only show the entries added after that commit.
 				</div>
 			</div>
-			<div data-changelog-entries={JSON.stringify(data.entries)}>
+			<div
+				data-changelog-entries={JSON.stringify(data.entries)}
+				data-changelog-head={data.headSha}
+			>
 				<ChangelogGraphic date={new Date()} entries={data.entries} />
 			</div>
 		</Main>

scripts/generate-changelog-image.ts

@@ -66,6 +66,8 @@ async function main() {
 		throw new Error(`No changelog canvas found at ${CHANGELOG_IMAGE_PAGE_URL}`);
 	}
 
+	await assertSameCheckout(page);
+
 	const entries = await parseEntries(page);
 	if (entries.length === 0) {
 		throw new Error(
@@ -118,6 +120,27 @@ async function main() {
 	}
 }
 
+/**
+ * The screenshotted page is whatever dev server holds the port, which can be another
+ * checkout of the repo whose entries are not the ones being shipped.
+ */
+async function assertSameCheckout(page: Page) {
+	const marker = page.locator("[data-changelog-head]");
+	const pageHead =
+		(await marker.count()) > 0
+			? await marker.getAttribute("data-changelog-head")
+			: null;
+	const localHead = (
+		await execFileAsync("git", ["rev-parse", "HEAD"])
+	).stdout.trim();
+
+	if (pageHead !== localHead) {
+		throw new Error(
+			`The server at ${CHANGELOG_IMAGE_PAGE_URL} is a different checkout of the repo: its HEAD is ${pageHead ?? "unknown"}, this one is at ${localHead}. Start a dev server from this folder and run again.`,
+		);
+	}
+}
+
 async function parseEntries(page: Page): Promise<ChangelogEntry[]> {
 	const json = await page
 		.locator("[data-changelog-entries]")