Log TOPIC messages

See [1].

[1]: 82c4ad8362/modules/log.cpp (L486)

logger.go

@@ -100,6 +100,12 @@ func formatMessage(msg *irc.Message) string {
 			reason = msg.Params[0]
 		}
 		return fmt.Sprintf("*** Quits: %s (%s@%s) (%s)", msg.Prefix.Name, msg.Prefix.User, msg.Prefix.Host, reason)
+	case "TOPIC":
+		var topic string
+		if len(msg.Params) > 1 {
+			topic = msg.Params[1]
+		}
+		return fmt.Sprintf("*** %s changes topic to '%s'", msg.Prefix.Name, topic)
 	case "MODE":
 		return fmt.Sprintf("*** %s sets mode: %s", msg.Prefix.Name, strings.Join(msg.Params[1:], " "))
 	case "NOTICE":

upstream.go

@@ -745,6 +745,7 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 		} else {
 			ch.Topic = ""
 		}
+		uc.appendLog(ch.Name, msg)
 		uc.forEachDownstream(func(dc *downstreamConn) {
 			params := []string{dc.marshalChannel(uc, name)}
 			if ch.Topic != "" {