fix(config): don't allow a platform-specific config filename for local platform (#41303)

As this currently does not make sense.

This may be revisited as part of #40970.

Author: jamietanna

lib/config/app-strings.spec.ts

@@ -25,4 +25,18 @@ describe('config/app-strings', () => {
       getConfigFileNames('github').includes('.github/renovate.json'),
     ).toBeTrue();
   });
+
+  it('does not allow the local platform to have an associated filename', () => {
+    const filenames = getConfigFileNames('local');
+
+    expect(filenames.includes('.local/renovate.json')).toBeFalse();
+    expect(filenames).toEqual([
+      'renovate.json',
+      'renovate.json5',
+      '.renovaterc',
+      '.renovaterc.json',
+      '.renovaterc.json5',
+      'package.json',
+    ]);
+  });
 });

lib/config/app-strings.ts

@@ -37,7 +37,7 @@ export function getConfigFileNames(platform?: PlatformId): string[] {
       return false;
     });
 
-    if (!['github', 'gitlab'].includes(platform)) {
+    if (!['github', 'gitlab'].includes(platform) && platform !== 'local') {
       filteredConfigFileNames.push(`.${platform}/renovate.json`);
       filteredConfigFileNames.push(`.${platform}/renovate.json5`);
     }