test: set name and email for repository fixture — heartwood

In fresh environments, without a global git config, the user.name and user.email will not be set for the fixture repository. This causes issues when tests are run and attempt to call git2::Signature::now – it will fail to read a user name and email for the commit.

To remedy this, the name and email are set for the repository when initialising it.

 /// Creates a regular repository at the given path with a couple of commits.
 pub fn repository<P: AsRef<Path>>(path: P) -> (git2::Repository, git2::Oid) {
     let repo = git2::Repository::init(path).unwrap();
     let sig = git2::Signature::new(
         "anonymous",
         "anonymous@radicle.xyz",
         &git2::Time::new(RADICLE_EPOCH, 0),
     )
     .unwrap();
     let user_name = "anonymous";
     let user_email = "anonymous@radicle.xyz";
     {
         let mut config = repo.config().unwrap();
         config.set_str("user.name", user_name).unwrap();
         config.set_str("user.email", user_email).unwrap();
     }
     let sig =
         git2::Signature::new(user_name, user_email, &git2::Time::new(RADICLE_EPOCH, 0)).unwrap();
     let head = git::initial_commit(&repo, &sig).unwrap();
     let tree = git::write_tree(Path::new("README"), "Hello World!\n".as_bytes(), &repo).unwrap();
     let oid = {