After #9504 we treat subcommands as commands, it's a good step, but it also introduced ambiguity, i.e. get|key is a bad command or a base command get? Maybe you will say it's a base command because get doesn't have subcommands, but it's very confused to users.

Here are some examples:

1. About COMMAND INFO
   • command info config|get returns subcommand config|get's info.
   • command info get|key returns base command get's info.
2. About ACL setuser
   • acl setuser test +config|get allows user execute subcommand config|get.
   • acl setuser test +config|get|dir allows user execute subcommand config|get with first arg dir.
   • acl setuser test +config|xxx returns error.
   • acl setuser test +get|key allows user execute base command get with first arg key.
   • acl setuser test +get|key1|key2 allows user execute base command get with the second arg key2, key1 lost.

To me the result is very confused, I thinks we should treat get|key as a bad command, and use another character instead of | to indicate the first arg.

BTW the first-arg rule is very difficult to understand IMHO, it's too flexible.