feat(commit): add ability to revert commit

lib/src/bindings/commit.dart

@@ -191,6 +191,45 @@ Pointer<git_oid> tree(Pointer<git_commit> commit) {
   return libgit2.git_commit_tree_id(commit);
 }
 
+/// Reverts the given commit against the given "our" commit, producing an index that
+/// reflects the result of the revert.
+///
+/// The returned index must be freed explicitly with `free()`.
+///
+/// Throws a [LibGit2Error] if error occured.
+Pointer<git_index> revertCommit(
+  Pointer<git_repository> repo,
+  Pointer<git_commit> revertCommit,
+  Pointer<git_commit> ourCommit,
+  int mainline,
+) {
+  final out = calloc<Pointer<git_index>>();
+  final opts = calloc<git_merge_options>();
+  final optsError =
+      libgit2.git_merge_options_init(opts, GIT_MERGE_OPTIONS_VERSION);
+
+  if (optsError < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  }
+
+  final error = libgit2.git_revert_commit(
+    out,
+    repo,
+    revertCommit,
+    ourCommit,
+    mainline,
+    opts,
+  );
+
+  calloc.free(opts);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    return out.value;
+  }
+}
+
 /// Get the repository that contains the commit.
 Pointer<git_repository> owner(Pointer<git_commit> commit) =>
     libgit2.git_commit_owner(commit);

lib/src/repository.dart

@@ -619,6 +619,24 @@ class Repository {
     return Index(result);
   }
 
+  /// Reverts the given commit against the given "our" commit, producing an index that
+  /// reflects the result of the revert.
+  ///
+  /// [mainline] is parent of the [revertCommit] if it is a merge (i.e. 1, 2).
+  ///
+  /// The returned index must be freed explicitly with `free()`.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  Index revertCommit(
+      {required Commit revertCommit, required Commit ourCommit, mainline = 0}) {
+    return Index(commit_bindings.revertCommit(
+      _repoPointer,
+      revertCommit.pointer,
+      ourCommit.pointer,
+      mainline,
+    ));
+  }
+
   /// Merges two trees, producing an index that reflects the result of the merge.
   /// The index may be written as-is to the working directory or checked out. If the index
   /// is to be converted to a tree, the caller should resolve any conflicts that arose as part

test/commit_test.dart

@@ -56,6 +56,21 @@ void main() {
       commit.free();
     });
 
+    test('successfully reverts commit', () {
+      final to = repo['78b8bf123e3952c970ae5c1ce0a3ea1d1336f6e8'] as Commit;
+      final from = repo['821ed6e80627b8769d170a293862f9fc60825226'] as Commit;
+      final index = repo.index;
+      expect(index.contains('dir/dir_file.txt'), true);
+
+      final revertIndex = repo.revertCommit(revertCommit: from, ourCommit: to);
+      expect(revertIndex.contains('dir/dir_file.txt'), false);
+
+      revertIndex.free();
+      index.free();
+      to.free();
+      from.free();
+    });
+
     test('successfully creates commit', () {
       final oid = Commit.create(
         repo: repo,