feat(revparse): add bindings and api

lib/src/bindings/revparse.dart

@@ -0,0 +1,85 @@
+import 'dart:ffi';
+import 'package:ffi/ffi.dart';
+import 'libgit2_bindings.dart';
+import '../error.dart';
+import '../util.dart';
+
+/// Parse 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.
+Pointer<git_revspec> revParse(
+  Pointer<git_repository> repo,
+  String spec,
+) {
+  final out = calloc<git_revspec>();
+  final specC = spec.toNativeUtf8().cast<Int8>();
+  final error = libgit2.git_revparse(out, repo, specC);
+
+  calloc.free(specC);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    return out;
+  }
+}
+
+/// Find 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.
+Pointer<git_object> revParseSingle(Pointer<git_repository> repo, String spec) {
+  final out = calloc<Pointer<git_object>>();
+  final specC = spec.toNativeUtf8().cast<Int8>();
+  final error = libgit2.git_revparse_single(
+    out,
+    repo,
+    specC,
+  );
+
+  calloc.free(specC);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    return out.value;
+  }
+}
+
+/// Find a single object and intermediate reference 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.
+List revParseExt(Pointer<git_repository> repo, String spec) {
+  final objectOut = calloc<Pointer<git_object>>();
+  final referenceOut = calloc<Pointer<git_reference>>();
+  final specC = spec.toNativeUtf8().cast<Int8>();
+  var result = [];
+  final error = libgit2.git_revparse_ext(objectOut, referenceOut, repo, specC);
+
+  calloc.free(specC);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    result.add(objectOut.value);
+    if (referenceOut.value != nullptr) {
+      result.add(referenceOut.value);
+    }
+    return result;
+  }
+}