doc: add fancy code comment for multi-pip expression

wait_for_pid_exit.sh

@@ -12,6 +12,11 @@ wait_for_pid_exit () {
 	waiting=0
 
 	debug_inline "waiting for $pid to exit "
+	#         show all pids
+	#         |       find just the $server_pid
+	#         |       |           don’t match on the previous grep
+	#         |       |           |            we don’t need the output
+	#         |       |           |            |
 	until ( ! ps ax | grep $pid | grep -v grep > /dev/null); do
 		if [ $waiting -eq $iterations ]; then
 			after=`expr $duration \* $iterations`