💥 Command Aliases

[phatblat]

Implements #153.

Opening this PR as a draft for discussion. I've got a simple/dumb implementation of aliases working in mas and you can see the behavior below. The install command was given an alias of i, but the help output lists the install command twice.

Available commands:

   account     Prints the primary account Apple ID
   help        Display general or command-specific help
   home        Opens MAS Preview app page in a browser
   info        Display app information from the Mac App Store
   install     Install from the Mac App Store
   install     Install from the Mac App Store
   ...

↪ sudo mas uninstall 803453959
Password:
==> App moved to trash: /private/var/root/.Trash/Slack 20-31-11-388.app

↪ mas i 803453959
==> Downloading Slack
#####################################################------- 88.0% Installing

This was achieved by:

1. Adding CommandProtocol.aliases
2. Registering commands again, once for each alias name

Modifying the CommandProtocol is a breaking change and each user of this library would need to add the alias property to every command, even if the command has no aliases. The 2nd item causes the command duplication but could be improved by extending the idea of an alias into the registry and auto-generating the help description with something like:

Available commands:

   install     Install from the Mac App Store
   i     Alias for install

Perhaps a better approach is to register aliases differently instead of modifying the model. Going to think some more about this but welcome any feedback or suggestions.

[phatblat]

Rebased onto master so compare view is much cleaner now.

[muescha]

and other solution would be a Wrapper for a command -

AliasCommandWrapper / Alias:

public struct Alias<ClientError: Error>: CommandProtocol {
	// [...]
	fileprivate init<C: CommandProtocol>(_ command: C, alias: String) where C.ClientError == ClientError {
		verb = alias
		function = "alias for '${command.verb}': {$command.function}"
		run = command.run
		usage = command.usage 
	}
}

usage:

registry.register(Alias(ListCommand(), alias: "L"))

drawback: the alias strings are not defined at the command class

[muescha]

Modifying the CommandProtocol is a breaking change and each user of this library would need to add the alias property to every command, even if the command has no aliases.

is it not possible to make the alias as optional, so that it not need to add and it is not a breaking change?

[muescha]

changes to display alias in commands list

[muescha]

Suggested change

	commandsByVerb[alias] = CommandWrapper(command)
	let wrappedCommand = CommandWrapper(command)
	wrappedCommand.verb = alias
	wrappedCommand.function = "alias for '${command.verb}': {$command.function}"
	commandsByVerb[alias] = wrappedCommand

[muescha]

Suggested change

	var aliases: [String] { get }
	var aliases: [String]? { get }

but let aliases be optional and not defined (null)

PS:
need to add

extension CommandProtocol {
    var aliases: [String]? { return nil }
}

or do just a default implementation:

extension CommandProtocol {
    var aliases: [String] { return [] }
}
``