feat(reference): add ability to compare references

lib/src/bindings/reference.dart

@@ -381,6 +381,12 @@ Pointer<git_reference> setTargetSymbolic(
   }
 }
 
+/// Compare two references.
+bool compare(Pointer<git_reference> ref1, Pointer<git_reference> ref2) {
+  final result = libgit2.git_reference_cmp(ref1, ref2);
+  return result == 0 ? true : false;
+}
+
 /// Ensure the reference name is well-formed.
 ///
 /// Valid reference names must follow one of two patterns:

lib/src/reference.dart

@@ -253,6 +253,15 @@ class Reference {
   /// Throws a [LibGit2Error] if the reference has changed from the time it was looked up.
   void delete() => bindings.delete(_refPointer);
 
+  @override
+  bool operator ==(other) {
+    return (other is Reference) &&
+        bindings.compare(_refPointer, other._refPointer);
+  }
+
+  @override
+  int get hashCode => _refPointer.address.hashCode;
+
   /// Releases memory allocated for reference object.
   void free() {
     bindings.free(_refPointer);

test/reference_test.dart

@@ -523,6 +523,21 @@ void main() {
       });
     });
 
+    test('checks equality', () {
+      final ref1 = Reference.get(repo, 'refs/heads/master');
+      final ref2 = Reference.get(repo, 'refs/heads/master');
+      final ref3 = Reference.get(repo, 'refs/heads/feature');
+
+      expect(ref1 == ref2, true);
+      expect(ref1 != ref2, false);
+      expect(ref1 == ref3, false);
+      expect(ref1 != ref3, true);
+
+      ref1.free();
+      ref2.free();
+      ref3.free();
+    });
+
     group('isValidName()', () {
       test('returns true for valid names', () {
         expect(Reference.isValidName('HEAD'), true);