Lazy load object format with command line and don't do it in OpenRepository (#29712)

Most time, when invoking `git.OpenRepository`, `objectFormat` will not
be used, so it's a waste to invoke commandline to get the object format.
This PR make it a lazy operation, only invoke that when necessary.

modules/git/repo_base_nogogit.go

@@ -71,11 +71,6 @@ func OpenRepository(ctx context.Context, repoPath string) (*Repository, error) {
 	repo.batchWriter, repo.batchReader, repo.batchCancel = CatFileBatch(ctx, repoPath)
 	repo.checkWriter, repo.checkReader, repo.checkCancel = CatFileBatchCheck(ctx, repoPath)
 
-	repo.objectFormat, err = repo.GetObjectFormat()
-	if err != nil {
-		return nil, err
-	}
-
 	return repo, nil
 }