feat(merge): add ability to cherry-pick commit

lib/src/bindings/merge.dart

@@ -67,11 +67,11 @@ void merge(
   int theirHeadsLen,
 ) {
   final mergeOpts = calloc<git_merge_options>(sizeOf<git_merge_options>());
-  libgit2.git_merge_options_init(mergeOpts, 1);
+  libgit2.git_merge_options_init(mergeOpts, GIT_MERGE_OPTIONS_VERSION);
 
   final checkoutOpts =
       calloc<git_checkout_options>(sizeOf<git_checkout_options>());
-  libgit2.git_checkout_options_init(checkoutOpts, 1);
+  libgit2.git_checkout_options_init(checkoutOpts, GIT_CHECKOUT_OPTIONS_VERSION);
   checkoutOpts.ref.checkout_strategy =
       git_checkout_strategy_t.GIT_CHECKOUT_SAFE +
           git_checkout_strategy_t.GIT_CHECKOUT_RECREATE_MISSING;
@@ -166,3 +166,19 @@ Pointer<git_index> mergeTrees(
     return out.value;
   }
 }
+
+/// Cherry-pick the given commit, producing changes in the index and working directory.
+///
+/// Throws a [LibGit2Error] if error occured.
+void cherryPick(Pointer<git_repository> repo, Pointer<git_commit> commit) {
+  final opts = calloc<git_cherrypick_options>(sizeOf<git_cherrypick_options>());
+  libgit2.git_cherrypick_options_init(opts, GIT_CHERRYPICK_OPTIONS_VERSION);
+  opts.ref.checkout_opts.checkout_strategy =
+      git_checkout_strategy_t.GIT_CHECKOUT_SAFE;
+
+  final error = libgit2.git_cherrypick(repo, commit, opts);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  }
+}

lib/src/repository.dart

@@ -608,4 +608,14 @@ class Repository {
 
     return Index(result);
   }
+
+  /// Cherry-picks the given commit, producing changes in the index and working directory.
+  ///
+  /// Any changes are staged for commit and any conflicts are written to the index. Callers
+  /// should inspect the repository's index after this completes, resolve any conflicts and
+  /// prepare a commit.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  void cherryPick(Commit commit) =>
+      merge_bindings.cherryPick(_repoPointer, commit.pointer);
 }

test/merge_test.dart

@@ -242,5 +242,15 @@ void main() {
         theirCommit.free();
       });
     });
+
+    test('successfully cherry-picks commit', () {
+      final cherry = repo['5aecfa0fb97eadaac050ccb99f03c3fb65460ad4'] as Commit;
+      repo.cherryPick(cherry);
+      expect(repo.state, GitRepositoryState.cherrypick.value);
+      final index = repo.index;
+      expect(index.conflicts, isEmpty);
+
+      index.free();
+    });
   });
 }