fix(rules): ignore cherry-picks in signed-off-by (#4625)

Before this change, the rule `signed-off-by` was rejecting cherry picked commits.
The cherry pick message wasn't appearing as the last line.
With this in place, the rule will treat cherry picked commits as regular commits.

Signed-off-by: Manuel Zedel <manuel.zedel@northern.tech>

Author: mzedel

@commitlint/rules/src/signed-off-by.test.ts

@@ -16,6 +16,15 @@ Signed-off-by:
 
 # Please enter the commit message for your changes. Lines starting
 # with '#' will be ignored, and an empty message aborts the commit.
+`,
+
+	withSignoffAndCherryPick: `test: subject
+
+message body
+
+Signed-off-by:
+
+(cherry picked from commit 1234567aB)
 `,
 };
 
@@ -26,6 +35,7 @@ const parsed = {
 	inSubject: parse(messages.inSubject),
 	inBody: parse(messages.inBody),
 	withSignoffAndComments: parse(messages.withSignoffAndComments),
+	withSignoffAndCherryPick: parse(messages.withSignoffAndCherryPick),
 };
 
 test('empty against "always signed-off-by" should fail', async () => {
@@ -109,3 +119,23 @@ test('inBody against "never signed-off-by" should succeed', async () => {
 	const expected = true;
 	expect(actual).toEqual(expected);
 });
+
+test("cherry pick marker should be ignored", async () => {
+	const [actual] = signedOffBy(
+		await parsed.withSignoffAndCherryPick,
+		"always",
+		"Signed-off-by:",
+	);
+	const expected = true;
+	expect(actual).toEqual(expected);
+});
+
+test('cherry pick marker with "never signed-off-by" should fail', async () => {
+	const [actual] = signedOffBy(
+		await parsed.withSignoffAndCherryPick,
+		"never",
+		"Signed-off-by:",
+	);
+	const expected = false;
+	expect(actual).toEqual(expected);
+});

@commitlint/rules/src/signed-off-by.ts

@@ -2,6 +2,8 @@ import message from "@commitlint/message";
 import toLines from "@commitlint/to-lines";
 import { SyncRule } from "@commitlint/types";
 
+const CHERRY_PICK_REGEX = /^\(cherry picked from commit [0-9a-f]{7,64}\)$/i;
+
 export const signedOffBy: SyncRule<string> = (
 	parsed,
 	when = "always",
@@ -11,6 +13,8 @@ export const signedOffBy: SyncRule<string> = (
 		(ln) =>
 			// skip comments
 			!ln.startsWith("#") &&
+			// skip cherry pick commits
+			!CHERRY_PICK_REGEX.test(ln.trim()) &&
 			// ignore empty lines
 			Boolean(ln),
 	);