Merge pull request 'A merge older than the watching is history, not news' (#127) from fix/a-merge-older-than-the-watching-is-history into main

An old merge past the first page of the forge's listing surfaced as newer pull requests were
updated, and was announced as if it had just happened; the mesh then rebuilt everything built from
that repository, once per old merge. The moment the watching began is kept with the record, and
only a merge made since is announced.

modules/gitea/index.ts

@@ -61,9 +61,17 @@ import { join } from "node:path";
 const mergedRecord = process.env.MESH_GITEA_STATE_DIR ? join(process.env.MESH_GITEA_STATE_DIR, "merged-announced.json") : null;
 const announced = new Set<string>();
 let primedMerges = false;
+// since is the moment the watching began: a merge made before it is history, whatever page of the
+// forge's listing it surfaces on. Without it, an old merge past the first page — pushed into view
+// as newer pull requests were updated — was announced as if it had just happened, and the mesh
+// rebuilt everything built from that repository, once per old merge (2026-09-28).
+let since = "";
 if (mergedRecord && existsSync(mergedRecord)) {
   try {
-    for (const sha of JSON.parse(readFileSync(mergedRecord, "utf8")) as string[]) announced.add(sha);
+    const kept = JSON.parse(readFileSync(mergedRecord, "utf8")) as string[] | { announced: string[]; since: string };
+    const list = Array.isArray(kept) ? kept : kept.announced;
+    for (const sha of list) announced.add(sha);
+    since = Array.isArray(kept) ? new Date().toISOString() : kept.since;
     primedMerges = true;
   } catch {
     // An unreadable record is treated as no record: prime again rather than re-announce history.
@@ -73,7 +81,7 @@ function keepAnnounced(): void {
   if (!mergedRecord) return;
   mkdirSync(join(mergedRecord, ".."), { recursive: true });
   const tmp = mergedRecord + ".tmp";
-  writeFileSync(tmp, JSON.stringify([...announced].slice(-2000)));
+  writeFileSync(tmp, JSON.stringify({ announced: [...announced].slice(-2000), since }));
   renameSync(tmp, mergedRecord);
 }
 async function pollMerged(client: GiteaClient): Promise<void> {
@@ -83,7 +91,10 @@ async function pollMerged(client: GiteaClient): Promise<void> {
     const pulls = await client.listPullRequests(repo.owner, repo.name, { state: "closed", sort: "recentupdate", limit: "20" });
     for (const pull of pulls) {
       if (!pull.merged || !pull.merge_commit_sha || announced.has(pull.merge_commit_sha)) continue;
-      if (primedMerges) {
+      // Announced only if merged since the watching began; recorded either way, so it is looked
+      // at once.
+      const fresh = !!pull.merged_at && !!since && pull.merged_at > since;
+      if (primedMerges && fresh) {
         await emit("pull.merged", {
           owner: repo.owner,
           repo: repo.name,
@@ -104,6 +115,7 @@ async function pollMerged(client: GiteaClient): Promise<void> {
       changed = true;
     }
   }
+  if (!primedMerges) since = new Date().toISOString();
   if (!primedMerges || changed) keepAnnounced();
   primedMerges = true;
 }