How do I pull all branches with NodeGit?

Question

I´m trying to do an update of my local repository.

According to the documentation, doing a fetchAll fetches all branches from the remote, which is what I´m currently doing. There is nothing like pullAll which automatically merges those remotes with my local ones.

My idea now was to get all branches after doing a fetchAll

 gitUpdate(url, options, repositoryPath, callback) {
        let repository = undefined;
        NodeGit.Repository.open(repositoryPath)
            .then(function (repo) {
                repository = repo;
                return repo.fetchAll(options.fetchOpts);
            })
            .then(function () {
                return repository.getReferenceNames(NodeGit.Reference.TYPE.LISTALL);
            })
            .then(function (branches) {
                /*
                 [ 'refs/heads/test',
                   'refs/heads/master',
                   'refs/remotes/origin/master',
                   'refs/remotes/origin/test' ] 
                */
                return console.log("branches", branches);
            })
            .then(function (fetched) {
                callback(null, fetched);
            }, function (err) {
                callback(err);
            });
    };

then iterate over them, filtering out matching ones and doing some string stuff to fit them into repository.mergeBranches("master", "origin/master");

While doing that I´m just thinking this can´t be seriously the way to go and there must be a shortcut somehow.

How do I simply sync the local repository with the remote one, including all branches, without cloning the repository again?