Document extends Command

[boblail]

Document and Command share 7 fields: arguments, options, commands, exitCodes, examples, interactive, and metadata.

The title and description fields of CliInfo serve the same purpose as the name and description fields of Command.

Document models the root command. Most CLIs model the root command the same way as subcommands — or with a subclass of the object used for subcommands. For example,

• alecthomas/kong (Go): the root CLI and commands are all modeled as Go structs using Kong's grammar
• oclif/oclif (TS): the root CLI and commands are all modeled as classes that extend Command
• spf13/cobra (Go): the root command and subcommands are all instances of *cobra.Command
• clap-rs/clap (Rust): the root and subcommands are all clap::Command values composed into a tree
• remkop/picocli (Java): the root command and subcommands are all @Command-annotated classes/objects
• commander-js/commander.js (JS): the “program” and its subcommands are all Command objects
• CLIUtils/CLI11 (C++): the root app and subcommands are all CLI::App objects (subcommands are Apps too!)
• dotnet/command-line-api (C#): the root command, System.CommandLine.RootCommand, extends System.CommandLine.Command
• pallets/click (Python): the root command, click.Group, extends click.Command

This change:

1. feat: adds summary to Command
2. BREAKING: renames CliInfo#title to CliInfo#name
3. BREAKING: hoists name, summary, and description up from CliInfo to Document
4. refactor: extends Document from Command

resolves #70

[patriksvensson]

@boblail Thanks for engaging.

Pull requests, however, require an open issue. An issue is opened when a discussion reaches a consensus. I will therefore close this PR. I hope you understand.