Page the announcer through every open pull request updated since its last look

A pass read only the 20 most recently updated open pull requests of a
repository, so a new head beyond them went unannounced and its merge check
never started (novox/hq issue 579). Pages stop at the floor; a sweep reads all.

modules/gitea/client.ts

@@ -342,8 +342,8 @@ export class GiteaClient {
   }
 
   /** **Every open pull request of a repository**, page by page (novox/hq ADR 0323 §4): what a trunk's move puts out of
-   *  date, however many are open — not the twenty most recently updated a pass announces from. Bounded at 20 pages
-   *  of 50; a repository with more is said, and the rest are left to the merge tool's own comparison. */
+   *  date, however many are open, whatever their update time (a pass announces from listOpenPullsSince). Bounded at
+   *  20 pages of 50; a repository with more is said, and the rest are left to the merge tool's own comparison. */
   async listOpenPulls(owner: string, repo: string): Promise<GiteaPull[]> {
     const out: GiteaPull[] = [];
     for (let page = 1; page <= 20; page++) {
@@ -355,6 +355,30 @@ export class GiteaClient {
     return out;
   }
 
+  /** **The open pull requests of a repository updated since a moment**, newest first, page by page (novox/hq issue
+   *  579): what a pass announces new heads from. The forge sorts `recentupdate` by update time, newest first, so the
+   *  paging stops at the first page that reaches back past `since`; with no moment — a sweep or the first pass —
+   *  every page is read. Bounded like listOpenPulls at 20 pages of 50. A pull request seen twice, pushed up a page
+   *  while the pages were read, is answered once. */
+  async listOpenPullsSince(owner: string, repo: string, since: string): Promise<GiteaPull[]> {
+    const out: GiteaPull[] = [];
+    const seen = new Set<number>();
+    const floor = since ? Date.parse(since) : NaN;
+    for (let page = 1; page <= 20; page++) {
+      const batch = await this.listPullRequests(owner, repo, { state: "open", sort: "recentupdate", limit: "50", page: String(page) });
+      for (const p of batch) {
+        if (seen.has(p.number)) continue;
+        seen.add(p.number);
+        out.push(p);
+      }
+      if (batch.length < 50) return out;
+      const oldest = batch[batch.length - 1]?.updated_at;
+      if (!Number.isNaN(floor) && oldest && Date.parse(oldest) < floor) return out;
+    }
+    console.error(`[gitea] ${owner}/${repo} has more than 1000 open pull requests updated since ${since || "ever"}; only the newest 1000 are read`);
+    return out;
+  }
+
   /** The commit a branch is at now: a trunk's head (novox/hq ADR 0323). */
   async branchHead(owner: string, repo: string, branch: string): Promise<string> {
     const b = await this.request<any>(`${repoPath(owner, repo)}/branches/${pathSegments("branch", branch)}`);