multi: make the next protocol version optional

loopd/config.go

@@ -149,6 +149,8 @@ type Config struct {
 	TotalPaymentTimeout time.Duration `long:"totalpaymenttimeout" description:"The timeout to use for off-chain payments."`
 	MaxPaymentRetries   int           `long:"maxpaymentretries" description:"The maximum number of times an off-chain payment may be retried."`
 
+	EnableExperimental bool `long:"experimental" description:"Enable experimental features: taproot HTLCs and MuSig2 loop out sweeps."`
+
 	Lnd *lndConfig `group:"lnd" namespace:"lnd"`
 
 	Server *loopServerConfig `group:"server" namespace:"server"`
@@ -185,6 +187,7 @@ func DefaultConfig() Config {
 		LoopOutMaxParts:     defaultLoopOutMaxParts,
 		TotalPaymentTimeout: defaultTotalPaymentTimeout,
 		MaxPaymentRetries:   defaultMaxPaymentRetries,
+		EnableExperimental:  false,
 		Lnd: &lndConfig{
 			Host:         "localhost:10009",
 			MacaroonPath: DefaultLndMacaroonPath,

loopd/daemon.go

@@ -348,6 +348,12 @@ func (d *Daemon) startWebServers() error {
 // this method fails with an error then no goroutine was started yet and no
 // cleanup is necessary. If it succeeds, then goroutines have been spawned.
 func (d *Daemon) initialize(withMacaroonService bool) error {
+	if d.cfg.EnableExperimental {
+		loopdb.EnableExperimentalProtocol()
+	}
+
+	log.Infof("Protocol version: %v", loopdb.CurrentProtocolVersion())
+
 	// If no swap server is specified, use the default addresses for mainnet
 	// and testnet.
 	if d.cfg.Server.Host == "" {