feat(commit): add ability to create commit

lib/src/bindings/commit.dart

@@ -3,6 +3,7 @@ import 'package:ffi/ffi.dart';
 import '../error.dart';
 import 'libgit2_bindings.dart';
 import '../util.dart';
+import 'oid.dart' as oid_bindings;
 
 /// Lookup a commit object from a repository.
 ///
@@ -20,6 +21,83 @@ Pointer<git_commit> lookup(Pointer<git_repository> repo, Pointer<git_oid> id) {
   }
 }
 
+/// Lookup a commit object from a repository, given a prefix of its identifier (short id).
+///
+/// Throws a [LibGit2Error] if error occured.
+Pointer<git_commit> lookupPrefix(
+  Pointer<git_repository> repo,
+  Pointer<git_oid> id,
+  int len,
+) {
+  final out = calloc<Pointer<git_commit>>();
+  final error = libgit2.git_commit_lookup_prefix(out, repo, id, len);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    return out.value;
+  }
+}
+
+/// Create new commit in the repository.
+///
+/// Throws a [LibGit2Error] if error occured.
+Pointer<git_oid> create(
+  Pointer<git_repository> repo,
+  String? updateRef,
+  Pointer<git_signature> author,
+  Pointer<git_signature> committer,
+  String? messageEncoding,
+  String message,
+  Pointer<git_tree> tree,
+  int parentCount,
+  List<String> parents,
+) {
+  final out = calloc<git_oid>();
+  final updateRefC = updateRef?.toNativeUtf8().cast<Int8>() ?? nullptr;
+  final messageEncodingC =
+      messageEncoding?.toNativeUtf8().cast<Int8>() ?? nullptr;
+  final messageC = message.toNativeUtf8().cast<Int8>();
+  late final Pointer<Pointer<git_commit>> parentsC;
+
+  if (parents.isNotEmpty) {
+    parentsC = calloc(parentCount);
+
+    for (var i = 0; i < parentCount; i++) {
+      final oid = oid_bindings.fromSHA(parents[i]);
+      final commit = lookup(repo, oid);
+      parentsC[i] = commit;
+    }
+  } else {
+    throw UnimplementedError(
+        'Writing commit without parents is not implemented');
+  }
+
+  final error = libgit2.git_commit_create(
+    out,
+    repo,
+    updateRefC,
+    author,
+    committer,
+    messageEncodingC,
+    messageC,
+    tree,
+    parentCount,
+    parentsC,
+  );
+
+  calloc.free(updateRefC);
+  calloc.free(messageEncodingC);
+  calloc.free(messageC);
+  calloc.free(parentsC);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    return out;
+  }
+}
+
 /// Get the encoding for the message of a commit, as a string representing a standard encoding name.
 ///
 /// The encoding may be NULL if the encoding header in the commit is missing;

lib/src/commit.dart

@@ -1,8 +1,11 @@
 import 'dart:ffi';
+
 import 'bindings/libgit2_bindings.dart';
 import 'bindings/commit.dart' as bindings;
+import 'repository.dart';
 import 'oid.dart';
 import 'signature.dart';
+import 'tree.dart';
 import 'util.dart';
 
 class Commit {
@@ -26,6 +29,58 @@ class Commit {
   /// Pointer to memory address for allocated commit object.
   late final Pointer<git_commit> _commitPointer;
 
+  /// Creates new commit in the repository.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  static Oid create({
+    required Repository repo,
+    required String message,
+    required Signature author,
+    required Signature commiter,
+    required String treeSHA,
+    required List<String> parentsSHA,
+    String? updateRef,
+    String? messageEncoding,
+  }) {
+    libgit2.git_libgit2_init();
+
+    final parentCount = parentsSHA.length;
+    late final Tree tree;
+
+    if (treeSHA.length == 40) {
+      final treeOid = Oid.fromSHA(treeSHA);
+      tree = Tree.lookup(
+        repo.pointer,
+        treeOid.pointer,
+      );
+    } else {
+      final odb = repo.odb;
+      final treeOid = Oid.fromShortSHA(treeSHA, odb);
+      tree = Tree.lookup(
+        repo.pointer,
+        treeOid.pointer,
+      );
+      odb.free();
+    }
+
+    final result = Oid(bindings.create(
+      repo.pointer,
+      updateRef,
+      author.pointer,
+      commiter.pointer,
+      messageEncoding,
+      message,
+      tree.pointer,
+      parentCount,
+      parentsSHA,
+    ));
+
+    tree.free();
+    libgit2.git_libgit2_init();
+
+    return result;
+  }
+
   /// Returns the encoding for the message of a commit, as a string
   /// representing a standard encoding name.
   String get messageEncoding => bindings.messageEncoding(_commitPointer);

lib/src/signature.dart

@@ -34,9 +34,11 @@ class Signature {
     }
   }
 
-  /// Pointer to memory address for allocated signature object.
   late final Pointer<git_signature> _signaturePointer;
 
+  /// Pointer to memory address for allocated signature object.
+  Pointer<git_signature> get pointer => _signaturePointer;
+
   /// Returns full name of the author.
   String get name => _signaturePointer.ref.name.cast<Utf8>().toDartString();