Help command produces invalid output with invalid flag

[kitd]

If you issue a help command on any plugin and add a flag, the help command fails and produces odd output.

Eg.

Entering bx pr help -n xxx or bx help -n xxx

Produces:

Incorrect Usage.

NAME:
   help - 

USAGE:

Expected behaviour would be for help to ignore any flag parsing, but if output was needed, something a bit more meaningful might be better.

[weieigao]

@kitd Why should help command ignore flag parsing? We allow plugin to have help subcommand to override default help, what if the help command do have some flags?
But I agree that we should refine the above output to make it more descriptive