Add clap for CLI help

[natemcintosh]

Goal

Add clap to add some CLI niceties. Print out help messages when run without any arguments (and when run with -h), and have an update command as the primary task.

Context

In a perfect world, duckup could one day be similar to rustup or juliaup in terms of the commands available. The first step on that road is just having some sort of CLI.

Required features

• Print a help message for -h, --help, or no argument
• Print a version number for -V or --version
• Have an duckup update command that actually runs the update

Specifications

• All arguments have help messages so auto-generated help works well
• Running with no arguments also prints the help message
• A update command that performs the update.

Out of scope

• Any other commands beyond update, help, and version
• Any new functionality beyond adding the CLI

Related documents

• clap examples