It was reported in #1817 that the `lotr_migration.git` repository we use
in `test/test_migrate.rb` is not a valid git repository on when clone,
causing the test suite to fail when run locally.
The reason is because there is no `.git/refs` directory, meaning it's
not really a valid git repository at all. I noticed that the `empty.git`
example repository has the same problem.
This commit simply ensures that the directory structure of these example
repositories are persisted in git.
benjamin wil
01005fdccf