Make the controller's event consumer from now, and give a stuck one a reset

A consumer made with the server's default replays everything a stream that
keeps history holds: the controller's EVENTS consumer, re-made that way,
replayed a week of merges and builds one at a time and held every new one
behind them. FromNow makes it start at the end; broker consumer-reset
re-makes a stuck one from now, refusing a work queue. hq issue 244.

cmd/mesh-controller/nodes.go

@@ -386,8 +386,12 @@ func brokerCommand(ctx context.Context, args []string) error {
 	if len(args) > 0 && args[0] == "accounts" {
 		return busAccounts(ctx, args[1:])
 	}
+	if len(args) > 0 && args[0] == "consumer-reset" {
+		return consumerReset(args[1:])
+	}
 	if len(args) == 0 || args[0] != "show" {
-		return errors.New("broker show | broker certificate [--check] --into <directory> | broker accounts --into <file>")
+		return errors.New("broker show | broker certificate [--check] --into <directory> | broker accounts --into <file> | " +
+			"broker consumer-reset <stream> <consumer>")
 	}
 	known, err := broker.FromEnvironment()
 	if errors.Is(err, broker.ErrNotConfigured) {
@@ -407,6 +411,34 @@ func brokerCommand(ctx context.Context, args []string) error {
 	return nil
 }
 
+// consumerReset re-makes one consumer on a stream that keeps history to start from now (novox/hq issue
+// 244): the way out of a consumer replaying a week of announcements, said rather than done by hand. A
+// person's act — what was pending is dropped — so it is a command, and nothing calls it on its own.
+func consumerReset(args []string) error {
+	if len(args) != 2 {
+		return errors.New("broker consumer-reset <stream> <consumer>, e.g. broker consumer-reset EVENTS controller")
+	}
+	address, err := broker.BusAddress()
+	if err != nil {
+		return err
+	}
+	js, err := broker.Dial(address)
+	if err != nil {
+		return fmt.Errorf("cannot reach the bus: %w", err)
+	}
+	defer js.Close()
+	before, after, err := js.ResetConsumer(args[0], args[1])
+	if err != nil {
+		return err
+	}
+	fmt.Printf("consumer %s on %s re-made to deliver from now\n", args[1], args[0])
+	fmt.Printf("  before: delivers %s, delivered to %d, acknowledged to %d, %d pending, %d unacknowledged\n",
+		before.DeliverPolicy, before.Delivered, before.AckFloor, before.Pending, before.AckPending)
+	fmt.Printf("  after:  delivers %s, %d pending; what was pending is dropped. A holder bound to it may need its "+
+		"process restarted to bind again\n", after.DeliverPolicy, after.Pending)
+	return nil
+}
+
 // heardFrom says when a node was last heard from, in a form somebody can act on.
 //
 // "never" and "an hour ago" are different answers and are kept different. A node that has never