feat(repository): add ability to compare Identity objects

lib/src/repository.dart

@@ -826,10 +826,14 @@ class RepositoryCallback {
   final String? originUrl;
 }
 
-class Identity {
+@immutable
+class Identity extends Equatable {
   /// Identity to use for reflogs.
   const Identity({required this.name, required this.email});
 
   final String name;
   final String email;
+
+  @override
+  List<Object?> get props => [name, email];
 }

test/repository_empty_test.dart

@@ -85,6 +85,7 @@ void main() {
         final identity = repo.identity;
         expect(identity.name, 'name');
         expect(identity.email, 'email@email.com');
+        expect(identity, equals(repo.identity));
       });
 
       test('unsets identity', () {