ngit.cs

var cloneUrl = ...;
var branchName = ...;

var git = Git.Init().SetDirectory(Location).Call();
Repository = git.GetRepository();

// Original code in question works, is shorter,
// but this is most likely the "proper" way to do it.
var config = Repository.GetConfig();
RemoteConfig remoteConfig = new RemoteConfig(config, "origin");
remoteConfig.AddURI(new URIish(cloneUrl));
// May use * instead of branch name to fetch all branches.
// Same as config.SetString("remote", "origin", "fetch", ...);
remoteConfig.AddFetchRefSpec(new RefSpec(
	"+refs/heads/" + Settings.Branch +
	":refs/remotes/origin/" + Settings.Branch));
remoteConfig.Update(config);
config.Save();

git.Fetch().Call();
git.BranchCreate().SetName(branchName).SetStartPoint("origin/" + branchName)
	.SetUpstreamMode(CreateBranchCommand.SetupUpstreamMode.TRACK).Call();
git.Checkout().SetName(branchName).Call();

// To update the branch:

git.Fetch().Call();
git.Reset().SetRef("origin/" + branchName).Call();