feat(rules): create header-full-stop rule

This is a simplified version of the subject-full-stop rule. Headers are always present, so we don’t need to check for empty-ness. If headers are not defined, the parser will throw with an error “expecting raw commit”.

@commitlint/rules/src/header-full-stop.js

@@ -0,0 +1,12 @@
+import message from '@commitlint/message';
+
+export default (parsed, when, value) => {
+	const {header} = parsed;
+	const negated = when === 'never';
+	const hasStop = header[header.length - 1] === value;
+
+	return [
+		negated ? !hasStop : hasStop,
+		message(['header', negated ? 'may not' : 'must', 'end with full stop'])
+	];
+};

@commitlint/rules/src/header-full-stop.test.js

@@ -0,0 +1,37 @@
+import test from 'ava';
+import parse from '@commitlint/parse';
+import check from './header-full-stop';
+
+const messages = {
+	with: `header.\n`,
+	without: `header\n`
+};
+
+const parsed = {
+	with: parse(messages.with),
+	without: parse(messages.without)
+};
+
+test('with against "always ." should succeed', async t => {
+	const [actual] = check(await parsed.with, 'always', '.');
+	const expected = true;
+	t.is(actual, expected);
+});
+
+test('with against "never ." should fail', async t => {
+	const [actual] = check(await parsed.with, 'never', '.');
+	const expected = false;
+	t.is(actual, expected);
+});
+
+test('without against "always ." should fail', async t => {
+	const [actual] = check(await parsed.without, 'always', '.');
+	const expected = false;
+	t.is(actual, expected);
+});
+
+test('without against "never ." should succeed', async t => {
+	const [actual] = check(await parsed.without, 'never', '.');
+	const expected = true;
+	t.is(actual, expected);
+});

@commitlint/rules/src/index.js

@@ -10,6 +10,7 @@ export default {
 	'footer-max-length': require('./footer-max-length'),
 	'footer-max-line-length': require('./footer-max-line-length'),
 	'footer-min-length': require('./footer-min-length'),
+	'header-full-stop': require('./header-full-stop'),
 	'header-max-length': require('./header-max-length'),
 	'header-min-length': require('./header-min-length'),
 	'references-empty': require('./references-empty'),