feat(repository): add ability to clone repository

lib/src/bindings/repository.dart

@@ -86,6 +86,53 @@ Pointer<git_repository> init(String path, bool isBare) {
   }
 }
 
+/// Clone a remote repository.
+///
+/// Throws a [LibGit2Error] if error occured.
+Pointer<git_repository> clone(
+  String url,
+  String localPath,
+  bool bare,
+  String checkoutBranch,
+) {
+  final out = calloc<Pointer<git_repository>>();
+  final urlC = url.toNativeUtf8().cast<Int8>();
+  final localPathC = localPath.toNativeUtf8().cast<Int8>();
+  final cloneOptions = calloc<git_clone_options>();
+  final cloneOptionsError =
+      libgit2.git_clone_options_init(cloneOptions, GIT_CLONE_OPTIONS_VERSION);
+
+  if (cloneOptionsError < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  }
+
+  final fetchOptions = calloc<git_fetch_options>();
+  final fetchOptionsError =
+      libgit2.git_fetch_options_init(fetchOptions, GIT_FETCH_OPTIONS_VERSION);
+
+  if (fetchOptionsError < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  }
+
+  cloneOptions.ref.bare = bare ? 1 : 0;
+  cloneOptions.ref.checkout_branch = checkoutBranch.isEmpty
+      ? nullptr
+      : checkoutBranch.toNativeUtf8().cast<Int8>();
+  cloneOptions.ref.fetch_opts = fetchOptions.ref;
+
+  final error = libgit2.git_clone(out, urlC, localPathC, cloneOptions);
+
+  calloc.free(urlC);
+  calloc.free(localPathC);
+  calloc.free(cloneOptions);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    return out.value;
+  }
+}
+
 /// Returns the path to the `.git` folder for normal repositories or the
 /// repository itself for bare repositories.
 String path(Pointer<git_repository> repo) {

lib/src/repository.dart

@@ -46,7 +46,9 @@ class Repository {
     _repoPointer = bindings.init(path, isBare);
   }
 
-  /// Initializes a new instance of the [Repository] class.
+  /// Initializes a new instance of the [Repository] class by opening repository
+  /// at provided [path].
+  ///
   /// For a standard repository, [path] should either point to the `.git` folder
   /// or to the working directory. For a bare repository, [path] should directly
   /// point to the repository folder.
@@ -60,6 +62,24 @@ class Repository {
     _repoPointer = bindings.open(path);
   }
 
+  /// Initializes a new instance of the [Repository] class by cloning a remote repository
+  /// at provided [url] into [localPath].
+  ///
+  /// [checkoutBranch] is the name of the branch to checkout after the clone. Defaults
+  /// to using the remote's default branch.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  Repository.clone({
+    required String url,
+    required String localPath,
+    bool bare = false,
+    String checkoutBranch = '',
+  }) {
+    libgit2.git_libgit2_init();
+
+    _repoPointer = bindings.clone(url, localPath, bare, checkoutBranch);
+  }
+
   late final Pointer<git_repository> _repoPointer;
 
   /// Pointer to memory address for allocated repository object.