feat(patch): add bindings and api

test/patch_test.dart

@@ -0,0 +1,180 @@
+import 'dart:io';
+import 'package:test/test.dart';
+import 'package:libgit2dart/libgit2dart.dart';
+import 'helpers/util.dart';
+
+void main() {
+  late Repository repo;
+  final tmpDir = '${Directory.systemTemp.path}/patch_testrepo/';
+  const oldBlob = '';
+  const newBlob = 'Feature edit\n';
+  const path = 'feature_file';
+  const oldBlobSha = 'e69de29bb2d1d6434b8b29ae775ad8c2e48c5391';
+  const newBlobSha = '9c78c21d6680a7ffebc76f7ac68cacc11d8f48bc';
+  const blobPatch = """
+diff --git a/feature_file b/feature_file
+index e69de29..9c78c21 100644
+--- a/feature_file
++++ b/feature_file
+@@ -0,0 +1 @@
++Feature edit
+""";
+
+  const blobPatchAdd = """
+diff --git a/feature_file b/feature_file
+new file mode 100644
+index 0000000..9c78c21
+--- /dev/null
++++ b/feature_file
+@@ -0,0 +1 @@
++Feature edit
+""";
+
+  const blobPatchDelete = """
+diff --git a/feature_file b/feature_file
+deleted file mode 100644
+index e69de29..0000000
+--- a/feature_file
++++ /dev/null
+""";
+
+  setUp(() async {
+    if (await Directory(tmpDir).exists()) {
+      await Directory(tmpDir).delete(recursive: true);
+    }
+    await copyRepo(
+      from: Directory('test/assets/testrepo/'),
+      to: await Directory(tmpDir).create(),
+    );
+    repo = Repository.open(tmpDir);
+  });
+
+  tearDown(() async {
+    repo.free();
+    await Directory(tmpDir).delete(recursive: true);
+  });
+
+  group('Patch', () {
+    test('successfully creates from buffers', () {
+      final patch = Patch.createFrom(
+        a: oldBlob,
+        b: newBlob,
+        aPath: path,
+        bPath: path,
+      );
+
+      expect(patch.size(), 14);
+      expect(patch.text, blobPatch);
+
+      patch.free();
+    });
+
+    test('successfully creates from one buffer (add)', () {
+      final patch = Patch.createFrom(
+        a: null,
+        b: newBlob,
+        aPath: path,
+        bPath: path,
+      );
+
+      expect(patch.text, blobPatchAdd);
+
+      patch.free();
+    });
+
+    test('successfully creates from one buffer (delete)', () {
+      final patch = Patch.createFrom(
+        a: oldBlob,
+        b: null,
+        aPath: path,
+        bPath: path,
+      );
+
+      expect(patch.text, blobPatchDelete);
+
+      patch.free();
+    });
+
+    test('successfully creates from blobs', () {
+      final a = repo[oldBlobSha] as Blob;
+      final b = repo[newBlobSha] as Blob;
+      final patch = Patch.createFrom(
+        a: a,
+        b: b,
+        aPath: path,
+        bPath: path,
+      );
+
+      expect(patch.text, blobPatch);
+
+      patch.free();
+    });
+
+    test('successfully creates from one blob (add)', () {
+      final b = repo[newBlobSha] as Blob;
+      final patch = Patch.createFrom(
+        a: null,
+        b: b,
+        aPath: path,
+        bPath: path,
+      );
+
+      expect(patch.text, blobPatchAdd);
+
+      patch.free();
+    });
+
+    test('successfully creates from one blob (delete)', () {
+      final a = repo[oldBlobSha] as Blob;
+      final patch = Patch.createFrom(
+        a: a,
+        b: null,
+        aPath: path,
+        bPath: path,
+      );
+
+      expect(patch.text, blobPatchDelete);
+
+      patch.free();
+    });
+
+    test('successfully creates from blob and buffer', () {
+      final a = repo[oldBlobSha] as Blob;
+      final patch = Patch.createFrom(
+        a: a,
+        b: newBlob,
+        aPath: path,
+        bPath: path,
+      );
+
+      expect(patch.text, blobPatch);
+
+      patch.free();
+    });
+
+    test('throws when argument is not Blob or String', () {
+      final commit = repo['fc38877b2552ab554752d9a77e1f48f738cca79b'] as Commit;
+      expect(
+        () => Patch.createFrom(
+          a: commit,
+          b: null,
+          aPath: 'file',
+          bPath: 'file',
+        ),
+        throwsA(isA<ArgumentError>()),
+      );
+
+      expect(
+        () => Patch.createFrom(
+          a: null,
+          b: commit,
+          aPath: 'file',
+          bPath: 'file',
+        ),
+        throwsA(isA<ArgumentError>()),
+      );
+
+      commit.free();
+    });
+  });
+}