If a command is ambiguous, you get this:
$ hg ve hg: command 've' is ambiguous: verify version [255]
If you typo a command, you get this:
$ hg comit hg: unknown command 'comit' (did you mean one of commit, incoming, mycommit?) [255]
But if you completely mistype a command so it no longer looks like any
existing commands, you get a full list of commands. That might be
useful the first time you use Mercurial, but after that it's probably
more annoying than help, especially if you have the pager enabled and
have a short terminal. Let's instead give a short hint telling the
user to run hg help for more help.