A merge says which files it changed

Every module built from a repository was rebuilt for a change to any of them: one merge in this
repository meant twenty-six builds, which is what exhausted a public registry's pull limit. The
forge lists the files a merge changed and the event carries them, from the watcher and from the
merge tool alike; a merge that changed more files than were asked for says so, and the mesh then
treats the whole repository as changed rather than guessing.

modules/gitea/client.ts

@@ -229,6 +229,17 @@ export class GiteaClient {
     return GiteaClient.mapPull(await this.request<any>(`/repos/${owner}/${repo}/pulls/${index}`));
   }
 
+  /** The files a merged pull request changed, as paths from the repository's root.
+   *
+   *  `limit` is what is asked for, and a merge that changed more says so rather than being read
+   *  page by page: what the mesh does with a partial list is treat the whole repository as changed,
+   *  so more pages would buy nothing. */
+  async listPullFiles(owner: string, repo: string, index: number, limit = 100): Promise<{ paths: string[]; truncated: boolean }> {
+    const files = await this.request<any[]>(`/repos/${owner}/${repo}/pulls/${index}/files?limit=${limit}`);
+    const paths = (files ?? []).map((f) => String(f?.filename ?? "")).filter((p) => p !== "");
+    return { paths, truncated: paths.length >= limit };
+  }
+
   async createPullRequest(
     owner: string,
     repo: string,