adds comment

create.sh

@@ -40,8 +40,10 @@ PING_MYSQL="mysqladmin \
   --user=${DB_USER} \
   --password=${DB_USER_PASSWORD} \
   --silent"
-# weird [: mysqld: unexpected operator when using PING_MYSQL but it works
-while [ ! $(docker exec ${DOCKER_PREFIX}-web /bin/sh -c "${PING_MYSQL}") ]
+# [: mysqld: unexpected operator when not using [
+# see: https://unix.stackexchange.com/a/482059
+#while [ ! $(docker exec ${DOCKER_PREFIX}-web /bin/sh -c "${PING_MYSQL}") ]
+while ! docker exec ${DOCKER_PREFIX}-web /bin/sh -c "${PING_MYSQL}"
 do
     echo Waiting for ${DOCKER_PREFIX}-db to accept connections…
     sleep 1