fix(rules): include possible body offset in footer leading blank

@commitlint/rules/src/footer-leading-blank.js

@@ -8,7 +8,10 @@ export default (parsed, when) => {
 	}
 
 	const negated = when === 'never';
-	const [leading] = toLines(parsed.raw).slice(toLines(parsed.body).length + 1);
+	const rawLines = toLines(parsed.raw);
+	const bodyLines = toLines(parsed.body);
+	const bodyOffset = bodyLines.length > 0 ? rawLines.indexOf(bodyLines[0]) : 1;
+	const [leading] = rawLines.slice(bodyLines.length + bodyOffset);
 
 	// Check if the first line of footer is empty
 	const succeeds = leading === '';

@commitlint/rules/src/footer-leading-blank.test.js

@@ -11,7 +11,8 @@ const messages = {
 		'feat(new-parser): introduces a new parsing library\n\nBREAKING CHANGE: new library does not support foo-construct',
 	with: 'test: subject\nbody\n\nBREAKING CHANGE: something important',
 	withMulitLine:
-		'test: subject\nmulti\nline\nbody\n\nBREAKING CHANGE: something important'
+		'test: subject\nmulti\nline\nbody\n\nBREAKING CHANGE: something important',
+	withDoubleNewLine: 'fix: some issue\n\ndetailed explanation\n\ncloses #123'
 };
 
 const parsed = {
@@ -21,7 +22,8 @@ const parsed = {
 	without: parse(messages.without),
 	withoutBody: parse(messages.withoutBody),
 	with: parse(messages.with),
-	withMulitLine: parse(messages.withMulitLine)
+	withMulitLine: parse(messages.withMulitLine),
+	withDoubleNewLine: parse(messages.withDoubleNewLine)
 };
 
 test('with simple message should succeed for empty keyword', async t => {
@@ -143,3 +145,15 @@ test('with blank line before footer and multiline body should succeed for "alway
 	const expected = true;
 	t.is(actual, expected);
 });
+
+test('with double blank line before footer and double line in body should fail for "never"', async t => {
+	const [actual] = footerLeadingBlank(await parsed.withDoubleNewLine, 'never');
+	const expected = false;
+	t.is(actual, expected);
+});
+
+test('with double blank line before footer and double line in body should succeed for "always"', async t => {
+	const [actual] = footerLeadingBlank(await parsed.withDoubleNewLine, 'always');
+	const expected = true;
+	t.is(actual, expected);
+});