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/test/pages.test.ts

@@ -22,3 +22,15 @@ test("every page of a pull request's files is read, though the forge caps a page
   assert.equal(got.truncated, false);
   assert.equal(new Set(got.paths).size, total);
 });
+
+test("a pass asks only the repositories that moved since the last look, every one before the first", async () => {
+  const { movedSince } = await import("../client.ts");
+  const repos = [
+    { full_name: "a/old", name: "old", owner: "a", private: false, html_url: "", updated_at: "2026-10-05T10:00:00Z" },
+    { full_name: "a/new", name: "new", owner: "a", private: false, html_url: "", updated_at: "2026-10-05T16:10:02Z" },
+    { full_name: "a/unknown", name: "unknown", owner: "a", private: false, html_url: "" },
+  ];
+  assert.deepEqual(movedSince(repos, "").map((r) => r.name), ["old", "new", "unknown"]);
+  assert.deepEqual(movedSince(repos, "2026-10-05T16:09:00.000Z").map((r) => r.name), ["new", "unknown"]);
+  assert.deepEqual(movedSince(repos, "2026-10-05T18:10:02+02:00").map((r) => r.name), ["new", "unknown"], "an offset is a moment, not a string");
+});