gitea: a merge poll looks only at repositories that moved, one pass at a time

With the poll the only announcer of a merge, its cost showed: every 30 s it
asked every repository for its pull requests, a pass outlasted the tick, and
passes piled up beside each other — a merge was announced four and a half
minutes late, and two passes at once could each announce it. A pass now asks
only repositories updated since a minute before the last look, and the next
pass starts when this one ends. hq issue 250.

modules/gitea/index.ts

@@ -14,7 +14,7 @@
 // the forge for an immediacy nobody asked for is not.
 
 import { emit } from "@novox/mesh-sdk/events";
-import { GiteaClient } from "./client.js";
+import { GiteaClient, movedSince } from "./client.js";
 
 // Without a way to a token — configured, or mintable with the admin account (token.ts) — there is
 // nothing to watch; log and stay quiet rather than crash the runtime. With one, the first poll mints
@@ -84,8 +84,16 @@ function keepAnnounced(): void {
   writeFileSync(tmp, JSON.stringify({ announced: [...announced].slice(-2000), since }));
   renameSync(tmp, mergedRecord);
 }
+// **Only the repositories that moved** (novox/hq issue 250). A merge is a push, and a push moves the
+// repository's update time; asking every repository for its pull requests on every tick took longer than the
+// tick itself, so ticks piled up and a merge was announced minutes late. A repository unchanged since a
+// minute before the last look is skipped — the minute absorbs the forge's clock against this one.
+let lastLook = "";
+const MARGIN_MS = 60_000;
 async function pollMerged(client: GiteaClient): Promise<void> {
-  const repos = await client.listAllRepos();
+  const began = new Date().toISOString();
+  const floor = lastLook && primedMerges ? new Date(Date.parse(lastLook) - MARGIN_MS).toISOString() : "";
+  const repos = movedSince(await client.listAllRepos(), floor);
   let changed = false;
   for (const repo of repos) {
     const pulls = await client.listPullRequests(repo.owner, repo.name, { state: "closed", sort: "recentupdate", limit: "20" });
@@ -124,6 +132,7 @@ async function pollMerged(client: GiteaClient): Promise<void> {
   if (!primedMerges) since = new Date().toISOString();
   if (!primedMerges || changed) keepAnnounced();
   primedMerges = true;
+  lastLook = began;
 }
 
 if (gitea) {
@@ -132,6 +141,9 @@ if (gitea) {
   // yet, the admin account refused on a restored forge) is one fact, and a recovery is worth a line.
   let failing: string | null = null;
   const tick = (fn: () => Promise<void>, everyMs: number): void => {
+    // **One pass at a time** (novox/hq issue 250): the next pass is scheduled when this one has ended, so a
+    // pass that outlasts its interval delays the next instead of running beside it — two passes at once
+    // could each announce the same merge before either recorded it.
     const run = (): void =>
       void fn()
         .then(() => {
@@ -142,8 +154,8 @@ if (gitea) {
           const why = err instanceof Error ? err.message : String(err);
           if (why !== failing) console.error(`[gitea] not watching until this clears — ${why}`);
           failing = why;
-        });
-    setInterval(run, everyMs);
+        })
+        .finally(() => setTimeout(run, everyMs));
     run();
   };
   tick(() => pollRepos(client), 60_000);