feat(packbuilder): add bindings and api

test/packbuilder_test.dart

@@ -0,0 +1,104 @@
+import 'dart:io';
+import 'package:libgit2dart/src/packbuilder.dart';
+import 'package:test/test.dart';
+import 'package:libgit2dart/libgit2dart.dart';
+import 'helpers/util.dart';
+
+void main() {
+  late Repository repo;
+  late Directory tmpDir;
+
+  setUp(() async {
+    tmpDir = await setupRepo(Directory('test/assets/testrepo/'));
+    repo = Repository.open(tmpDir.path);
+  });
+
+  tearDown(() async {
+    repo.free();
+    await tmpDir.delete(recursive: true);
+  });
+
+  group('PackBuilder', () {
+    test('successfully initializes', () {
+      final packbuilder = PackBuilder(repo);
+
+      expect(packbuilder, isA<PackBuilder>());
+      expect(packbuilder.length, 0);
+
+      packbuilder.free();
+    });
+
+    test('successfully adds objects', () {
+      final packbuilder = PackBuilder(repo);
+      final odb = repo.odb;
+
+      packbuilder.add(odb.objects[0]);
+      expect(packbuilder.length, 1);
+
+      packbuilder.add(odb.objects[1]);
+      expect(packbuilder.length, 2);
+
+      odb.free();
+      packbuilder.free();
+    });
+
+    test('successfully adds objects recursively', () {
+      final packbuilder = PackBuilder(repo);
+      final oid = Oid.fromSHA(repo: repo, sha: 'f17d0d48');
+
+      packbuilder.addRecursively(oid);
+      expect(packbuilder.length, 3);
+
+      packbuilder.free();
+    });
+
+    test('successfully sets number of threads', () {
+      final packbuilder = PackBuilder(repo);
+
+      expect(packbuilder.setThreads(1), 1);
+
+      packbuilder.free();
+    });
+
+    test('successfully packs with default arguments', () {
+      final odb = repo.odb;
+      final objectsCount = odb.objects.length;
+      final writtenCount = repo.pack();
+
+      expect(writtenCount, objectsCount);
+
+      odb.free();
+    });
+
+    test('successfully packs into provided path', () {
+      final odb = repo.odb;
+      final objectsCount = odb.objects.length;
+      Directory('${repo.workdir}test-pack').createSync();
+
+      final writtenCount = repo.pack(path: '${repo.workdir}test-pack');
+      expect(writtenCount, objectsCount);
+      expect(
+        Directory('${repo.workdir}test-pack').listSync().isNotEmpty,
+        true,
+      );
+
+      odb.free();
+    });
+
+    test('successfully packs with provided packDelegate', () {
+      void packDelegate(PackBuilder packBuilder) {
+        for (var branchName in repo.branches.list()) {
+          final branch = repo.references['refs/heads/$branchName'];
+          for (var commit in repo.log(sha: branch.target.sha)) {
+            packBuilder.addRecursively(commit.id);
+            commit.free();
+          }
+          branch.free();
+        }
+      }
+
+      final writtenCount = repo.pack(packDelegate: packDelegate);
+      expect(writtenCount, 18);
+    });
+  });
+}