[470246] Change sys tree print output on USR2.

Thanks to Yun Wu.

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=470246

ChangeLog.txt

@@ -20,6 +20,8 @@ Broker:
 - Add systemd startup notification and services. Closes #471053.
 - Reduce unnecessary malloc and memcpy when receiving a message and storing
   it. Closes #470258.
+- Change sys tree printing output. This format shouldn't be relied upon and
+  may change at any time. Closes #470246.
 
 Client library:
 - Outgoing messages with QoS>1 are no longer retried after a timeout period.

src/subs.c

@@ -599,23 +599,25 @@ void sub__tree_print(struct mosquitto__subhier *root, int level)
 	struct mosquitto__subhier *branch;
 	struct mosquitto__subleaf *leaf;
 
-	for(i=0; i<level*2; i++){
-		printf(" ");
-	}
-	printf("%s", UHPA_ACCESS_TOPIC(root));
-	leaf = root->subs;
-	while(leaf){
-		if(leaf->context){
-			printf(" (%s, %d)", leaf->context->id, leaf->qos);
-		}else{
-			printf(" (%s, %d)", "", leaf->qos);
+	if(level > 1){
+		for(i=0; i<(level-2)*2; i++){
+			printf(" ");
 		}
-		leaf = leaf->next;
+		printf("%s", UHPA_ACCESS_TOPIC(root));
+		leaf = root->subs;
+		while(leaf){
+			if(leaf->context){
+				printf(" (%s, %d)", leaf->context->id, leaf->qos);
+			}else{
+				printf(" (%s, %d)", "", leaf->qos);
+			}
+			leaf = leaf->next;
+		}
+		if(root->retained){
+			printf(" (r)");
+		}
+		printf("\n");
 	}
-	if(root->retained){
-		printf(" (r)");
-	}
-	printf("\n");
 
 	branch = root->children;
 	while(branch){