Collapse help into expandable command topics

plugins/storage/commands

@@ -4,11 +4,25 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 
 case "$1" in
   help | storage:help)
-    cat<<EOF
+    help_content_func () {
+      declare desc="return help_content string"
+      cat<<help_content
     storage:list <app>, List bind mounts for app's container(s) (host:container)
     storage:mount <app> <host-dir:container-dir>, Create a new bind mount
     storage:unmount <app> <host-dir:container-dir>, Remove an existing bind mount
-EOF
+help_content
+    }
+
+    if [[ $1 = "shell:help" ]] ; then
+        echo -e 'Usage: dokku storage:COMMAND'
+        echo ''
+        echo 'Mount local volume / directories inside containers.'
+        echo ''
+        echo 'Additional commands:'
+        help_content_func | sort | column -c2 -t -s,
+    else
+        help_content_func
+    fi
     ;;
 
   *)