nodegit-pull.js

function createBranch(repo, newBranchName, remoteName, remoteBranch) {
    var remoteRefBase = 'refs/remotes/' + remoteName;
    var remoteRefName = remoteRefBase + '/' + remoteBranch;
    var remoteRefHead = remoteRefBase + '/' + 'HEAD';
    
    return NodeGit.Reference.symbolicCreate(repo, remoteRefHead, remoteRefName, 1, 'Setting HEAD')
        .then(function () {
            return repo.getReference(remoteRefName);
        })
        .then(function (remoteRef) {
            // Create new branch based on the remote ref
            return repo.createBranch(newBranchName, remoteRef.target());
        })
        .then(function (branchRef) {
            // checkout branch to update working directory
            return repo.checkoutBranch(branchRef);
        });
    });
}

// example

repo.fetchAll().then(function () {
    return createBranch(repo, 'new', 'new', 'master');
}).then(function () {
    return repo.mergeBranches('new', 'new/master');
}).then(function () {
    return repo.checkoutBranch('master');
}).then(function () {
    return repo.mergeBranches('master', 'new');
})