 						Command.Description(
 							name: "update",
 							overview: "Update package dependencies",
-							callback: echo,
+							callback: nil,
 							options: [
 								Option.Description(
 									flag: .long("repin"),

			" and parameters \(evaluation.parameters)"
		)
	}

	func testMarkdownExample() {
		func echo(evaluation: Command.Evaluation) throws {
			print(
				"\(evaluation.name) evaluated with " +
				"options: \(evaluation.options) " +
				"and parameters \(evaluation.parameters)"
			)
		}

		let swiftCommand =
		Command.Description(
			name: "swift",
			overview: "Swift Program",
			callback: echo,
			options: [],
			subCommands: [
				Command.Description(
					name: "package",
					overview: "Perform operations on Swift packages",
					callback: echo,
					options: [
						Option.Description(
							flag: .both(short: "v", long: "verbose"),


	}

	func echo(evaluation: Command.Evaluation) throws {
		print(
			"\(evaluation.name) evaluated with " +
