feat(patch): add binding and API method for git_patch_line_stats (#39)

lib/src/bindings/patch.dart

@@ -177,6 +177,31 @@ Map<String, Object> hunk({
   return {'hunk': out.value, 'linesN': linesN};
 }
 
+/// Get line counts of each type in a patch.
+Map<String, int> lineStats(Pointer<git_patch> patch) {
+  final context = calloc<Uint64>();
+  final insertions = calloc<Uint64>();
+  final deletions = calloc<Uint64>();
+  libgit2.git_patch_line_stats(
+    context,
+    insertions,
+    deletions,
+    patch,
+  );
+
+  final result = {
+    'context': context.value,
+    'insertions': insertions.value,
+    'deletions': deletions.value,
+  };
+
+  calloc.free(context);
+  calloc.free(insertions);
+  calloc.free(deletions);
+
+  return result;
+}
+
 /// Get data about a line in a hunk of a patch.
 Pointer<git_diff_line> lines({
   required Pointer<git_patch> patchPointer,

lib/src/patch.dart

@@ -42,8 +42,6 @@ class Patch {
     int contextLines = 3,
     int interhunkLines = 0,
   }) {
-    libgit2.git_libgit2_init();
-
     _patchPointer = bindings.fromBlobs(
       oldBlobPointer: oldBlob?.pointer,
       oldAsPath: oldBlobPath,
@@ -127,6 +125,8 @@ class Patch {
     int contextLines = 3,
     int interhunkLines = 0,
   }) {
+    libgit2.git_libgit2_init();
+
     _patchPointer = bindings.fromBuffers(
       oldBuffer: oldBuffer,
       oldAsPath: oldBufferPath,
@@ -148,8 +148,6 @@ class Patch {
   ///
   /// Throws a [LibGit2Error] if error occured.
   Patch.fromDiff({required Diff diff, required int index}) {
-    libgit2.git_libgit2_init();
-
     _patchPointer = bindings.fromDiff(diffPointer: diff.pointer, index: index);
   }
 
@@ -158,6 +156,17 @@ class Patch {
   /// Pointer to memory address for allocated patch object.
   Pointer<git_patch> get pointer => _patchPointer;
 
+  /// Line counts of each type in a patch.
+  PatchStats get stats {
+    final result = bindings.lineStats(_patchPointer);
+
+    return PatchStats(
+      context: result['context']!,
+      insertions: result['insertions']!,
+      deletions: result['deletions']!,
+    );
+  }
+
   /// Content of a patch as a single diff text.
   ///
   /// Throws a [LibGit2Error] if error occured.
@@ -216,3 +225,27 @@ class Patch {
   @override
   String toString() => 'Patch{size: ${size()}, delta: $delta}';
 }
+
+/// Line counts of each type in a patch.
+class PatchStats {
+  const PatchStats({
+    required this.context,
+    required this.insertions,
+    required this.deletions,
+  });
+
+  /// Count of context lines.
+  final int context;
+
+  /// Count of insertion lines.
+  final int insertions;
+
+  /// Count of deletion lines.
+  final int deletions;
+
+  @override
+  String toString() {
+    return 'PatchStats{context: $context, insertions: $insertions, '
+        'deletions: $deletions}';
+  }
+}

test/patch_test.dart

@@ -163,6 +163,23 @@ index e69de29..0000000
       expect(() => Patch(nullptr).text, throwsA(isA<LibGit2Error>()));
     });
 
+    test('returns line counts of each type in a patch', () {
+      final patch = Patch.fromBuffers(
+        oldBuffer: oldBuffer,
+        newBuffer: newBuffer,
+        oldBufferPath: path,
+        newBufferPath: path,
+      );
+
+      final stats = patch.stats;
+      expect(stats.context, equals(0));
+      expect(stats.insertions, equals(1));
+      expect(stats.deletions, equals(0));
+      expect(stats.toString(), contains('PatchStats{'));
+
+      patch.free();
+    });
+
     test('returns string representation of Patch object', () {
       final patch = Patch.fromBuffers(
         oldBuffer: oldBuffer,