feat(revparse): add bindings and api

lib/src/revparse.dart

@@ -0,0 +1,91 @@
+import 'dart:ffi';
+import 'bindings/libgit2_bindings.dart';
+import 'bindings/revparse.dart' as bindings;
+import 'commit.dart';
+import 'reference.dart';
+import 'repository.dart';
+import 'enums.dart';
+
+class RevParse {
+  /// Finds a single object and intermediate reference (if there is one) by a [spec] revision string.
+  ///
+  /// See `man gitrevisions`, or https://git-scm.com/docs/git-rev-parse.html#_specifying_revisions
+  /// for information on the syntax accepted.
+  ///
+  /// In some cases (@{<-n>} or <branchname>@{upstream}), the expression may point to an
+  /// intermediate reference. When such expressions are being passed in, reference_out will be
+  /// valued as well.
+  ///
+  /// The returned object and reference should be released when no longer needed.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  RevParse.ext(Repository repo, String spec) {
+    final pointers = bindings.revParseExt(repo.pointer, spec);
+    object = Commit(pointers[0].cast<git_commit>());
+    if (pointers.length == 2) {
+      reference = Reference(repo.pointer, pointers[1].cast<git_reference>());
+    } else {
+      reference = null;
+    }
+  }
+
+  /// Object found by a revision string.
+  late final Commit object;
+
+  /// Intermediate reference found by a revision string.
+  late final Reference? reference;
+
+  /// Finds a single object, as specified by a [spec] revision string.
+  /// See `man gitrevisions`, or https://git-scm.com/docs/git-rev-parse.html#_specifying_revisions
+  /// for information on the syntax accepted.
+  ///
+  /// The returned object should be released when no longer needed.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  static Commit single(Repository repo, String spec) {
+    return Commit(bindings.revParseSingle(repo.pointer, spec).cast());
+  }
+
+  /// Parses a revision string for from, to, and intent.
+  ///
+  /// See `man gitrevisions` or https://git-scm.com/docs/git-rev-parse.html#_specifying_revisions
+  /// for information on the syntax accepted.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  static RevSpec range(Repository repo, String spec) {
+    return RevSpec(bindings.revParse(repo.pointer, spec));
+  }
+}
+
+class RevSpec {
+  /// Initializes a new instance of [RevSpec] class from provided
+  /// pointer to revspec object in memory.
+  RevSpec(this._revSpecPointer);
+
+  /// Pointer to memory address for allocated revspec object.
+  late final Pointer<git_revspec> _revSpecPointer;
+
+  /// The left element of the revspec; must be freed by the user.
+  Commit get from => Commit(_revSpecPointer.ref.from.cast());
+
+  /// The right element of the revspec; must be freed by the user.
+  Commit? get to {
+    if (_revSpecPointer.ref.to == nullptr) {
+      return null;
+    } else {
+      return Commit(_revSpecPointer.ref.to.cast());
+    }
+  }
+
+  /// The intent of the revspec.
+  GitRevParse get flags {
+    final flag = _revSpecPointer.ref.flags;
+    if (flag == 1) {
+      return GitRevParse.single;
+    } else if (flag == 2) {
+      return GitRevParse.range;
+    } else {
+      return GitRevParse.mergeBase;
+    }
+  }
+}