Rename alias to shortFlag

[tommy-mitchell]

Closes #109.

flag.alias is now flag.shortFlag for users:

const cli = meow(`
	Usage
	  $ foo <input>

	Options
	  --rainbow, -r  Include a rainbow

	Examples
	  $ foo unicorns --rainbow
	  🌈 unicorns 🌈
`, {
	importMeta: import.meta,
	flags: {
		rainbow: {
			type: 'boolean',
			shortFlag: 'r'
		}
	}
});

An extra check was added to buildParserFlags() to ensure compatibility with minimist-options:

// index.js

const buildParserFlags = ({flags, booleanDefault}) => {
	const parserFlags = {};

	for (const [flagKey, flagValue] of Object.entries(flags)) {
		const flag = {...flagValue};

		// `buildParserOptions` expects `flag.alias`
		if (flag.shortFlag) {
			flag.alias = flag.shortFlag;
			delete flag.shortFlag;
		}

		// ...
	}

	return parserFlags;
}

[tommy-mitchell]

Should flag.aliases be a part of this PR as well, or a separate one?

[sindresorhus]

Should flag.aliases be a part of this PR as well, or a separate one?

Separate

[sindresorhus]

Can you make it throw a user-friendly error when alias option is used?

[tommy-mitchell]

Can you make it throw a user-friendly error when alias option is used?

meow({
	importMeta,
	flags: {
		foo: {
			type: 'string',
			alias: 'f',
		},
		bar: {
			type: 'string',
			alias: 'b',
		},
		baz: {
			type: 'string',
			shortFlag: 'z',
		},
	},
});
//=> 'The option `alias` has been renamed to `shortFlag`. The following flags need to be updated: `foo`, `bar`'

[sindresorhus]

Perfect 👍