feat(cli): add "--config" option support

@commitlint/cli/fixtures/specify-config-file/commitlint.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+	rules: {
+		'header-max-length': [2, 'always', 4]
+	}
+};

@commitlint/cli/fixtures/specify-config-file/config/commitlint.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+	rules: {
+		'type-enum': [2, 'never', ['foo']]
+	}
+};

@commitlint/cli/src/cli.js

@@ -12,7 +12,7 @@ const pkg = require('../package');
 const help = require('./help');
 
 const configuration = {
-	string: ['cwd', 'from', 'to', 'edit', 'extends', 'parser-preset'],
+	string: ['cwd', 'from', 'to', 'edit', 'extends', 'parser-preset', 'config'],
 	boolean: ['help', 'version', 'quiet', 'color'],
 	alias: {
 		c: 'color',
@@ -22,13 +22,15 @@ const configuration = {
 		t: 'to',
 		q: 'quiet',
 		h: 'help',
+		g: 'config',
 		v: 'version',
 		x: 'extends',
 		p: 'parser-preset'
 	},
 	description: {
 		color: 'toggle colored output',
 		cwd: 'directory to execute in',
+		config: 'path to the config file',
 		edit:
 			'read last commit message from the specified file or fallbacks to ./.git/COMMIT_EDITMSG',
 		extends: 'array of shareable configurations to extend',
@@ -41,6 +43,7 @@ const configuration = {
 	default: {
 		color: true,
 		cwd: process.cwd(),
+		config: null,
 		edit: false,
 		from: null,
 		to: null,
@@ -96,7 +99,8 @@ async function main(options) {
 		throw err;
 	}
 
-	const loaded = await core.load(getSeed(flags), {cwd: flags.cwd});
+	const loadOpts = {cwd: flags.cwd, file: flags.config};
+	const loaded = await core.load(getSeed(flags), loadOpts);
 	const parserOpts = selectParserOpts(loaded.parserPreset);
 	const opts = parserOpts ? {parserOpts} : {parserOpts: {}};
 

@commitlint/cli/src/cli.test.js

@@ -59,6 +59,14 @@ test('should fail for input from stdin with rule from rc', async t => {
 	t.is(actual.code, 1);
 });
 
+test('should work with --config option', async t => {
+	const file = 'config/commitlint.config.js';
+	const cwd = await git.bootstrap('fixtures/specify-config-file');
+	const actual = await cli(['--config', file], {cwd})('foo: bar');
+	t.true(actual.stdout.includes('type must not be one of [foo]'));
+	t.is(actual.code, 1);
+});
+
 test('should fail for input from stdin with rule from js', async t => {
 	const cwd = await git.bootstrap('fixtures/extends-root');
 	const actual = await cli(['--extends', './extended'], {cwd})('foo: bar');

@commitlint/core/fixtures/specify-config-file/commitlint.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+	rules: {
+		'foo': 'hello',
+		'bar': 'world'
+	}
+};

@commitlint/core/fixtures/specify-config-file/config/commitlint.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+	rules: {
+		'foo': 'bar'
+	}
+};

@commitlint/core/src/load.js

@@ -12,7 +12,7 @@ const w = (a, b) => (Array.isArray(b) ? b : undefined);
 const valid = input => pick(input, 'extends', 'rules', 'parserPreset');
 
 export default async (seed = {}, options = {cwd: process.cwd()}) => {
-	const loaded = await loadConfig(options.cwd);
+	const loaded = await loadConfig(options.cwd, options.file);
 	const base = loaded.filepath ? path.dirname(loaded.filepath) : options.cwd;
 
 	// Merge passed config with file based options
@@ -78,9 +78,10 @@ export default async (seed = {}, options = {cwd: process.cwd()}) => {
 	}, preset);
 };
 
-async function loadConfig(cwd) {
+async function loadConfig(cwd, configPath) {
 	const explorer = cosmiconfig('commitlint', {
-		rcExtensions: true
+		rcExtensions: true,
+		configPath: configPath ? path.resolve(cwd, configPath) : null
 	});
 
 	const local = await explorer.load(cwd);

@commitlint/core/src/load.test.js

@@ -16,6 +16,13 @@ test('uses seed as configured', async t => {
 	t.is(actual.rules.foo, 'bar');
 });
 
+test('rules should be loaded from specify config file', async t => {
+	const file = 'config/commitlint.config.js';
+	const cwd = await git.bootstrap('fixtures/specify-config-file');
+	const actual = await load({}, {cwd, file});
+	t.is(actual.rules.foo, 'bar');
+});
+
 test('uses seed with parserPreset', async t => {
 	const cwd = await git.bootstrap('fixtures/parser-preset');
 	const {parserPreset: actual} = await load(