* Ensure example git repos are valid
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.
* Run `test_migrate` tests on CI
Now that we've resolved the issue with the invalid git repository in the
parent commit, we can run all of the tests in our CI environment.
benjamin wil
2dfe103687