message: HEAD must be used as updateRef
diff: @@ -241,11 +241,13 @@ bool Commit::revert() const {
  return !error;
  }
  -bool Commit::amend(const Signature& author, const Signature& committer, const QString& commitMessage) const {
  +bool Commit::amend(const Signature &author, const Signature &committer,
  + const QString &commitMessage) const {
  Repository repo = this->repo();
  git_tree *tree = nullptr;
  git_oid *oid;
  - int error = git_commit_amend(oid, *this, NULL, &*author, &*committer, NULL, commitMessage.toUtf8(), tree);
  + int error = git_commit_amend(oid, *this, "HEAD", &*author, &*committer, NULL,
  + commitMessage.toUtf8(), tree);
  emit repo.notifier()->referenceUpdated(repo.head());
  return !error;
  }
  