[feature request] Alias for parent command should apply to subcommands

[jsumners]

prog
  .command('foo')
  .describe('Top level command')
  .alias('f')
  .action(() => console.log('see `app foo --help`'))

prog
  .command('foo bar')
  .describe('A subcommand')
  .action(() => console.log('did a thing'))

prog
  .command('foo baz <a>')
  .describe('Another subcommand')
  .action((a) => console.log('did another thing', a))

Given the above, each of the following should work:

• prog foo
• prog foo bar
• prog foo baz 1
• prog f
• prog f bar
• prog f baz 1