Keep delivery check standard output the answer alone and answer the request id asked (issue 1311)

cmd/mesh-controller/delivery.go

@@ -902,10 +902,16 @@ func deliveryCommand(ctx context.Context, args []string) error {
 		if *group == "" && len(members) == 1 {
 			// One head, checked again as the forge's announcement would have it (a recheck): the controller's
 			// own path for a pull request, run because the delivery's owner asked.
-			if err := sayingOnTheBus(ctx, inv, func() error { return (following{open: open, oneShot: true}).PullUpdated(ctx, members[0].pull()) }); err != nil {
+			// Its prose goes to standard error: standard output is the answer's JSON alone, or the seat verb
+			// reads no answer from it (novox/hq issue 1311).
+			var asked string
+			if err := sayingOnTheBus(ctx, inv, func() (err error) {
+				asked, err = (following{open: open, oneShot: true}).pullUpdated(ctx, members[0].pull(), os.Stderr)
+				return err
+			}); err != nil {
 				return err
 			}
-			return answer(map[string]any{"rechecked": members[0].ID})
+			return answer(recheckAnswer(asked, members[0].ID))
 		}
 		if *group == "" || len(members) < 2 {
 			return errors.New("delivery check --group <id> --members <json> (two heads or more), or --members <one head>")
@@ -1156,7 +1162,7 @@ func askGroupCheck(ctx context.Context, open *stores, group string, members []or
 	if failing, cyclic, err := cycleVerdict(ctx, group, members, reach, edges, entries); err != nil {
 		return "", err
 	} else if cyclic {
-		sayChecked(ctx, failing)
+		sayChecked(ctx, os.Stderr, failing)
 		return failing.ID, nil
 	}
 	primary := groupPrimary(members, reach)
@@ -1376,3 +1382,9 @@ func overNATS(conn *nats.Conn) (link.Bus, error) {
 	}
 	return link.OverNATS{Conn: conn, JS: js}, nil
 }
+
+// recheckAnswer is what `delivery check` answers for one head: the id of the check asked of the build seat (empty when
+// the controller said the verdict itself and asked nothing), which mesh-delivery reads, and the head rechecked.
+func recheckAnswer(asked, member string) map[string]any {
+	return map[string]any{"asked": asked, "rechecked": member}
+}