update util script to be able to derive schedule from CHANGELOG

generateReleasePlan.mjs

@@ -0,0 +1,70 @@
+#!/usr/bin/env node
+
+// Generate Release Plan table for a given release line.
+// Usage:
+// node --harmony-temporal generateReleasePlan.mjs xx
+// or
+// node --harmony-temporal generateReleasePlan.mjs path/to/CHANGELOG_Vxx.md
+
+import { open, readFile } from 'node:fs/promises'
+const schedule = JSON.parse(await readFile(new URL('./schedule.json', import.meta.url), 'utf-8'));
+
+let [,, version] = process.argv;
+
+console.log(`_Draft schedule - all dates subject to change_
+
+Version | Release Date | Releaser(s)
+--------|--------------| -------------`);
+
+let lastReleaseDate;
+if (isNaN(version)) {
+  const existingReleases = [];
+  const releaseTitle = /^## (\d{4}-\d{2}-\d{2}), Version (\d+\.\d+\.\d+) ([^,]+), (.+)$/;
+  const securityRelease = /^This is a security release\.$/;
+  const fd = await open(version, 'r');
+  let releaseType
+  for await (const line of fd.readLines()) {
+	const releaseTitleMatch = releaseTitle.exec(line);
+	if (releaseTitleMatch) {
+		const [, date, version, type, releasers] = releaseTitleMatch;
+  		lastReleaseDate ??= Temporal.PlainDate.from(date);
+		const versionStr = type === '(Current)' && type !== releaseType ? `${version} (LTS transition)` : version;
+		existingReleases.unshift(` ${versionStr} | ${date} | ${releasers}`)
+		releaseType = type;
+	} else if (securityRelease.test(line)) {
+		existingReleases[0] = existingReleases[0].replace(/^([^|]+) \|/, "$1 (Security) |");
+	}
+  }
+  console.log(existingReleases.join('\n'))
+
+  version = existingReleases[0].slice(1, existingReleases[0].indexOf('.'));
+}
+const versionKey = `v${version}`;
+
+if (!Object.hasOwn(schedule, versionKey)) {
+	throw new Error(`Unknown version ${version}, accepted values are ${Object.keys(schedule)}`);
+}
+
+const { start, maintenance, lts } = schedule[versionKey];
+
+const ltsDateTime = lts && Temporal.PlainDate.from(lts);
+const maintenanceDateTime = Temporal.PlainDate.from(maintenance);
+
+const isNowDuringLTS = lts && Temporal.PlainDate.compare(Temporal.Now.plainDateTimeISO(), ltsDateTime) > 0;
+const weeks = isNowDuringLTS ? 4 : 2;
+
+const startOfCycle = lastReleaseDate?.add({ weeks }) ?? (isNowDuringLTS ? ltsDateTime : Temporal.PlainDate.from(start));
+const endOfCycle = isNowDuringLTS ? maintenanceDateTime : ltsDateTime || maintenanceDateTime;
+
+
+for (let i = startOfCycle; Temporal.PlainDate.compare(i, endOfCycle) === -1; i = i.add({ weeks })) {
+	console.log(` ${version}.x.x |  ${i}  | `);
+}
+
+if (lts && (!lastReleaseDate || Temporal.PlainDate.compare(maintenance, lastReleaseDate) > 0)) {
+	console.log(
+		`${version}.x.x (${isNowDuringLTS ? 'Maintenance' : 'LTS'} transition) |  ${
+			isNowDuringLTS ? maintenance : lts
+		}  | ${isNowDuringLTS ? '_No release_' : ''}`,
+	);
+}