feat(repository): add ability to pass credentials in callbacks argument

lib/src/features.dart

@@ -0,0 +1,18 @@
+import 'util.dart';
+import 'git_types.dart';
+
+class Features {
+  /// Returns list of compile time options for libgit2.
+  static List<GitFeature> get list {
+    var result = <GitFeature>[];
+    final featuresInt = libgit2.git_libgit2_features();
+
+    for (var flag in GitFeature.values) {
+      if (featuresInt & flag.value == flag.value) {
+        result.add(flag);
+      }
+    }
+
+    return result;
+  }
+}