Add error() for displaying errors from client code

[shadowspawn]

Pull Request

Problem

People adding extra error checks do not have a way to take advantage of the error configuration built into Commander such as: .configureOutput(), .exitOverride(), .showHelpAfterError().

There have not been many requests for this, but we do now have quite rich error handling which clients can use for their own errors too.

Related: #1358 #1632

Solution

Provide a low level routine that is also used by Commander itself. Refactor private ._displayError() into public .error(). Change the signature to make the error id code and exitCode optional so can be called with just a message.

if (cmd.opts().good && cmd.opts().bad)
  cmd.error('error: specify just one of "--good" and "--bad"');

ChangeLog

• add error() for generating errors from client code just like Commander generated errors, with support for .configureOutput(), .exitOverride(), and .showHelpAfterError()

[abetomo]

awesome!

[shadowspawn]

Thanks @abetomo
I will do another prerelease soon. No other changes in mind!

[shadowspawn]

.error() is included in prerelease Commander v9.0.0-1.

[shadowspawn]

Commander v9 has been released.