feat: semantic pr title for migrationPRs (#16490)

* generate PR title using ConfigMigrationCommitMessageFactory

* add test

lib/workers/repository/config-migration/pr/index.spec.ts

@@ -169,6 +169,40 @@ describe('workers/repository/config-migration/pr/index', () => {
       expect(platform.createPr.mock.calls[0][0].prBody).toMatchSnapshot();
     });
 
+    it('creates non-semantic PR title', async () => {
+      await ensureConfigMigrationPr(
+        {
+          ...config,
+          prHeader: '\r\r\nThis should not be the first line of the PR',
+          prFooter:
+            'There should be several empty lines at the end of the PR\r\n\n\n',
+        },
+        migratedData
+      );
+      expect(platform.createPr).toHaveBeenCalledTimes(1);
+      expect(platform.createPr.mock.calls[0][0].prTitle).toBe(
+        'Migrate config renovate.json'
+      );
+    });
+
+    it('creates semantic PR title', async () => {
+      await ensureConfigMigrationPr(
+        {
+          ...config,
+          commitMessagePrefix: '',
+          semanticCommits: 'enabled',
+          prHeader: '\r\r\nThis should not be the first line of the PR',
+          prFooter:
+            'There should be several empty lines at the end of the PR\r\n\n\n',
+        },
+        migratedData
+      );
+      expect(platform.createPr).toHaveBeenCalledTimes(1);
+      expect(platform.createPr.mock.calls[0][0].prTitle).toBe(
+        'chore(config): migrate config renovate.json'
+      );
+    });
+
     it('creates PR with footer and header using templating', async () => {
       config.baseBranch = 'some-branch';
       config.repository = 'test';

lib/workers/repository/config-migration/pr/index.ts

@@ -11,6 +11,7 @@ import { joinUrlParts } from '../../../../util/url';
 import { getPlatformPrOptions } from '../../update/pr';
 import { prepareLabels } from '../../update/pr/labels';
 import { addParticipants } from '../../update/pr/participants';
+import { ConfigMigrationCommitMessageFactory } from '../branch/commit-message';
 import type { MigratedData } from '../branch/migrated-data';
 import { getMigrationBranchName } from '../common';
 
@@ -24,7 +25,12 @@ export async function ensureConfigMigrationPr(
     'configuration-options/#configmigration'
   );
   const branchName = getMigrationBranchName(config);
-  const prTitle = 'Migrate Renovate config';
+  const commitMessageFactory = new ConfigMigrationCommitMessageFactory(
+    config,
+    migratedConfigData.filename
+  );
+
+  const prTitle = commitMessageFactory.create().toString();
   const existingPr = await platform.getBranchPr(branchName);
   const filename = migratedConfigData.filename;
   logger.debug('Filling in config migration PR template');