PreRepositoryHook access affected files content

Hi guys,
I’ve got a hook: PreRepositoryHook
My question is, how can I access, the content of the affected files ?
Thank you in advance!

public class RestrictionHook implements PreRepositoryHook

public RepositoryHookResult preUpdate(@Nonnull PreRepositoryHookContext preRepositoryHookContext, @Nonnull RepositoryHookRequest repositoryHookRequest) {

    return RepositoryHookResult.accepted();    }

public void onEnd(@Nonnull PreRepositoryHookContext context, @Nonnull RepositoryHookRequest request, @Nonnull RepositoryHookResult result) {