feat(platform/github): flag to control whether PRs can be edited by m…

…aintainers if `forkToken`is set (#19771)

docs/usage/configuration-options.md

@@ -894,6 +894,22 @@ Renovate follows tags _strictly_, this can cause problems when a tagged stream i
 For example: you're following the `next` tag, but later the stream you actually want is called `stable` instead.
 If `next` is no longer getting updates, you must switch your `followTag` to `stable` to get updates again.
 
+## forkModeDisallowMaintainerEdits
+
+Use `forkModeDisallowMaintainerEdits` to disallow maintainers from editing Renovate's pull requests when in fork mode.
+
+If GitHub pull requests are created from a [fork repository](https://docs.github.com/en/get-started/quickstart/fork-a-repo), the PR author can decide to allow upstream repository to modify the PR directly.
+
+Allowing maintainers to edit pull requests directly is helpful when Renovate pull requests require additional changes.
+The reviewer can simply push to the pull request without having to create a new PR. [More details here](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork).
+
+You may decide to disallow edits to Renovate pull requests in order to workaround issues in Renovate where modified fork branches are not deleted properly: [See this issue](https://github.com/renovatebot/renovate/issues/16657).
+If this option is enabled, reviewers will need to create a new PR if additional changes are needed.
+
+<!-- prettier-ignore -->
+!!! note
+    This option is only relevant if you set `forkToken`.
+
 ## gitAuthor
 
 You can customize the Git author that's used whenever Renovate creates a commit.

lib/config/options/index.ts

@@ -1929,6 +1929,14 @@ const options: RenovateOptions[] = [
     default: false,
     supportedPlatforms: ['gitlab'],
   },
+  {
+    name: 'forkModeDisallowMaintainerEdits',
+    description:
+      'Disallow maintainers to push to Renovate pull requests when running in fork mode.',
+    type: 'boolean',
+    supportedPlatforms: ['github'],
+    default: false,
+  },
   {
     name: 'confidential',
     description:

lib/config/types.ts

@@ -230,6 +230,7 @@ export interface RenovateConfig
   postUpdateOptions?: string[];
   prConcurrentLimit?: number;
   prHourlyLimit?: number;
+  forkModeDisallowMaintainerEdits?: boolean;
 
   defaultRegistryUrls?: string[];
   registryUrls?: string[] | null;

lib/modules/platform/github/index.spec.ts

@@ -274,7 +274,7 @@ describe('modules/platform/github/index', () => {
     repository: string,
     forkExisted: boolean,
     forkResult = 200,
-    forkDefaulBranch = 'master'
+    forkDefaultBranch = 'master'
   ): void {
     scope
       // repo info
@@ -307,7 +307,7 @@ describe('modules/platform/github/index', () => {
               {
                 full_name: 'forked/repo',
                 owner: { login: 'forked' },
-                default_branch: forkDefaulBranch,
+                default_branch: forkDefaultBranch,
               },
             ]
           : []
@@ -2180,6 +2180,96 @@ describe('modules/platform/github/index', () => {
       expect(pr).toMatchObject({ number: 123 });
     });
 
+    describe('with forkToken', () => {
+      let scope: httpMock.Scope;
+
+      beforeEach(async () => {
+        scope = httpMock.scope(githubApiHost);
+        forkInitRepoMock(scope, 'some/repo', false);
+        scope.get('/user').reply(200, {
+          login: 'forked',
+        });
+        scope.post('/repos/some/repo/forks').reply(200, {
+          full_name: 'forked/repo',
+          default_branch: 'master',
+        });
+
+        await github.initRepo({
+          repository: 'some/repo',
+          forkToken: 'true',
+        });
+      });
+
+      it('should allow maintainer edits if explicitly enabled via options', async () => {
+        scope
+          .post(
+            '/repos/some/repo/pulls',
+            // Ensure the `maintainer_can_modify` option is set in the REST API request.
+            (body) => body.maintainer_can_modify === true
+          )
+          .reply(200, {
+            number: 123,
+            head: { repo: { full_name: 'some/repo' }, ref: 'some-branch' },
+          });
+        const pr = await github.createPr({
+          sourceBranch: 'some-branch',
+          targetBranch: 'main',
+          prTitle: 'PR title',
+          prBody: 'PR can be edited by maintainers.',
+          labels: null,
+          platformOptions: {
+            forkModeDisallowMaintainerEdits: false,
+          },
+        });
+        expect(pr).toMatchObject({ number: 123 });
+      });
+
+      it('should allow maintainer edits if not explicitly set', async () => {
+        scope
+          .post(
+            '/repos/some/repo/pulls',
+            // Ensure the `maintainer_can_modify` option is `false` in the REST API request.
+            (body) => body.maintainer_can_modify === true
+          )
+          .reply(200, {
+            number: 123,
+            head: { repo: { full_name: 'some/repo' }, ref: 'some-branch' },
+          });
+        const pr = await github.createPr({
+          sourceBranch: 'some-branch',
+          targetBranch: 'main',
+          prTitle: 'PR title',
+          prBody: 'PR *cannot* be edited by maintainers.',
+          labels: null,
+        });
+        expect(pr).toMatchObject({ number: 123 });
+      });
+
+      it('should disallow maintainer edits if explicitly disabled', async () => {
+        scope
+          .post(
+            '/repos/some/repo/pulls',
+            // Ensure the `maintainer_can_modify` option is `false` in the REST API request.
+            (body) => body.maintainer_can_modify === false
+          )
+          .reply(200, {
+            number: 123,
+            head: { repo: { full_name: 'some/repo' }, ref: 'some-branch' },
+          });
+        const pr = await github.createPr({
+          sourceBranch: 'some-branch',
+          targetBranch: 'main',
+          prTitle: 'PR title',
+          prBody: 'PR *cannot* be edited by maintainers.',
+          labels: null,
+          platformOptions: {
+            forkModeDisallowMaintainerEdits: true,
+          },
+        });
+        expect(pr).toMatchObject({ number: 123 });
+      });
+    });
+
     describe('automerge', () => {
       const createdPrResp = {
         number: 123,

lib/modules/platform/github/index.ts

@@ -1499,7 +1499,8 @@ export async function createPr({
   // istanbul ignore if
   if (config.forkToken) {
     options.token = config.forkToken;
-    options.body.maintainer_can_modify = true;
+    options.body.maintainer_can_modify =
+      platformOptions?.forkModeDisallowMaintainerEdits !== true;
   }
   logger.debug({ title, head, base, draft: draftPR }, 'Creating PR');
   const ghPr = (

lib/modules/platform/types.ts

@@ -92,6 +92,7 @@ export type PlatformPrOptions = {
   bbUseDefaultReviewers?: boolean;
   gitLabIgnoreApprovals?: boolean;
   usePlatformAutomerge?: boolean;
+  forkModeDisallowMaintainerEdits?: boolean;
 };
 export interface CreatePRConfig {
   sourceBranch: string;

lib/workers/repository/update/pr/index.ts

@@ -51,6 +51,7 @@ export function getPlatformPrOptions(
     azureWorkItemId: config.azureWorkItemId,
     bbUseDefaultReviewers: config.bbUseDefaultReviewers,
     gitLabIgnoreApprovals: config.gitLabIgnoreApprovals,
+    forkModeDisallowMaintainerEdits: config.forkModeDisallowMaintainerEdits,
     usePlatformAutomerge,
   };
 }