Auto merge of #3618 - sbeckeriv:3473-new-subcommand-doc-update, r=alexcrichton

Update new command help doc

Resolves #3473

Dearest reviewer,

I hope that all is well in rustland. I was reviewing some open issues
and saw this update to the help text for the new command. I have added
the suggested help text from issue #3473. I formated to the message to
match the publish bin's job flag.

Thank you for your time,
Becker