Replace use of arguments.length

[shadowspawn]

Pull Request

Problem

The use of arguments.length to test for parameters in the get/set routines leads to misleading editor auto-generated help. This is a documentation problem for the author rather than a functional problem.

For example, Visual Studio Code displays extra parameters for any routine which has a call to arguments.length:

(method) Command.name(str?: string, ...args: any[]): string | Command

Solution

Replace uses of arguments.length with test of parameter against undefined. Now VSC displays:

(method) Command.name(str?: string): string | Command

Also:

• tightened special case behaviour in alias for adding alias for executable subcommand
• refactored usage to only calculate the default usage string when required

[abetomo]

LGTM!