add user as co-author in case of conflict

Author: aduh95

lib/update-v8/backport.js

@@ -9,6 +9,7 @@ import { ListrEnquirerPromptAdapter } from '@listr2/prompt-adapter-enquirer';
 import { shortSha } from '../utils.js';
 
 import { getCurrentV8Version } from './common.js';
+import { forceRunAsync } from '../run.js';
 
 export async function checkOptions(options) {
   if (options.sha.length > 1 && options.squash) {
@@ -78,9 +79,9 @@ function commitSquashedBackport() {
   };
 };
 
-const commitTask = (patch, ...extraArgs) => async(ctx) => {
+const commitTask = (patch, extraArgs, trailers) => async(ctx) => {
   const messageTitle = formatMessageTitle([patch]);
-  const messageBody = formatMessageBody(patch, false);
+  const messageBody = formatMessageBody(patch, false, trailers);
   await ctx.execGitNode('add', ['deps/v8']);
   await ctx.execGitNode('commit', [
     ...ctx.gpgSign, ...extraArgs,
@@ -92,10 +93,22 @@ function amendHEAD(patch) {
   return {
     title: 'Amend/commit',
     task: async(ctx) => {
+      let coAuthor;
       if (patch.hadConflicts) {
+        const getGitConfigEntry = async(configKey) => {
+          const output = await forceRunAsync('git', ['config', configKey], {
+            ignoreFailure: false,
+            captureStdout: true,
+            spawnArgs: { cwd: ctx.nodeDir }
+          });
+          return output.trim();
+        };
         await ctx.execGitNode('am', [...ctx.gpgSign, '--continue']);
+        coAuthor = `\nCo-authored-by: ${
+          await getGitConfigEntry('user.name')} <${
+          await getGitConfigEntry('user.email')}>`;
       }
-      await commitTask(patch, '--amend')(ctx);
+      await commitTask(patch, ['--amend'], coAuthor)(ctx);
     }
   };
 }
@@ -125,12 +138,12 @@ function formatMessageTitle(patches) {
   }
 }
 
-function formatMessageBody(patch, prefixTitle) {
+function formatMessageBody(patch, prefixTitle, trailers = '') {
   const indentedMessage = patch.message.replace(/\n/g, '\n    ');
   const body =
     'Original commit message:\n\n' +
     `    ${indentedMessage}\n\n` +
-    `Refs: https://github.com/v8/v8/commit/${patch.sha}`;
+    `Refs: https://github.com/v8/v8/commit/${patch.sha}${trailers}`;
 
   if (prefixTitle) {
     const action = patch.hadConflicts ? 'Backport' : 'Cherry-pick';