fix(git): gracefully handle not a git repository failure

lib/workers/repository/error.spec.ts

@@ -93,6 +93,13 @@ describe('workers/repository/error', () => {
       const res = await handleError(config, gitError);
       expect(res).toEqual(EXTERNAL_HOST_ERROR);
     });
+    it('rewrites git fatal error', async () => {
+      const gitError = new Error(
+        'fatal: not a git repository (or any parent up to mount point /mnt)\nStopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).\n'
+      );
+      const res = await handleError(config, gitError);
+      expect(res).toEqual(REPOSITORY_TEMPORARY_ERROR);
+    });
     it('handles unknown error', async () => {
       const res = await handleError(config, new Error('abcdefg'));
       expect(res).toEqual(UNKNOWN_ERROR);

lib/workers/repository/error.ts

@@ -183,6 +183,10 @@ export default async function handleError(
     // rewrite this error
     return EXTERNAL_HOST_ERROR;
   }
+  if (err.message.includes('fatal: not a git repository')) {
+    delete config.branchList; // eslint-disable-line no-param-reassign
+    return REPOSITORY_TEMPORARY_ERROR;
+  }
   // Swallow this error so that other repositories can be processed
   logger.error({ err }, `Repository has unknown error`);
   // delete branchList to avoid cleaning up branches