A byond like interface for asyncrounously cloning or fetching a repo at a given path and checking out a given reference

GetRefExample.cs

using LibGit2Sharp;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace GetRefExample
{
	sealed class GetRefExample
	{
		const string Done = "DONE";
		const string NotDone = "NOTDONE";

		long jobCounter;

		Dictionary<string, Task> jobs = new Dictionary<string, Task>();
		Dictionary<string, CancellationTokenSource> cancelTokens = new Dictionary<string, CancellationTokenSource>();
		Dictionary<string, Exception> errors = new Dictionary<string, Exception>();

		Task GetRefImpl(string jobName, string remoteUrl, string refName, string outputDirectory, CancellationToken cancellationToken) => Task.Factory.StartNew(() =>
		{
			Repository repo = null;
			try
			{
				string remoteName;
				if (!Repository.IsValid(outputDirectory))
				{
					cancellationToken.ThrowIfCancellationRequested();

					Directory.Delete(outputDirectory, recursive: true);
					cancellationToken.ThrowIfCancellationRequested();

					Repository.Clone(remoteUrl, outputDirectory);
					cancellationToken.ThrowIfCancellationRequested();

					repo = new Repository(outputDirectory);
					remoteName = "origin";
				}
				else
				{
					repo = new Repository(outputDirectory);
					cancellationToken.ThrowIfCancellationRequested();

					repo.RemoveUntrackedFiles();
					cancellationToken.ThrowIfCancellationRequested();

					var remoteToUse = repo.Network.Remotes.First();
					remoteName = remoteToUse.Name;
					cancellationToken.ThrowIfCancellationRequested();

					Commands.Fetch(repo, remoteName, remoteToUse.FetchRefSpecs.Select(x => x.Specification), new FetchOptions(), "Fetch");
				}
				cancellationToken.ThrowIfCancellationRequested();

				Commands.Checkout(repo, remoteName + '/' + refName, new CheckoutOptions
				{
					CheckoutModifiers = CheckoutModifiers.Force
				});
			}
			catch (OperationCanceledException) { }
			catch (Exception e)
			{
				lock (errors)
					errors.Add(jobName, e);
			}
			finally
			{
				repo?.Dispose();
			}
		}, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current);

		public string Init()
		{
			foreach (var I in cancelTokens)
			{
				var cts = I.Value;
				cts.Cancel();
				cts.Dispose();
			}
			cancelTokens.Clear();

			foreach (var I in jobs)
				I.Value.Wait();
			jobs.Clear();

			errors.Clear();

			return null;
		}

		public string CancelGetRef(string jobName)
		{
			if (!cancelTokens.TryGetValue(jobName, out var cts))
				return null;
			cancelTokens.Remove(jobName);
			cts.Cancel();
			return Done;
		}

		public string GetRefFinished(string jobName)
		{
			if (!jobs.TryGetValue(jobName, out var job))
				return null;

			if (!job.IsCompleted)
				return NotDone;

			jobs.Remove(jobName);
			var cts = cancelTokens[jobName];
			cancelTokens.Remove(jobName);
			cts.Dispose();

			lock (errors)
				if (errors.TryGetValue(jobName, out var exception))
				{
					errors.Remove(jobName);
					return exception.Message;
				}

			return Done;
		}

		public string BeginGetRef(string remoteUrl, string refName, string outputDirectory)
		{
			var jobName = (++jobCounter).ToString();

			var cts = new CancellationTokenSource();
			lock (cancelTokens)
				cancelTokens.Add(jobName, cts);
			lock(jobs)
				jobs.Add(jobName, GetRefImpl(jobName, remoteUrl, refName, outputDirectory, cts.Token));

			return jobName;
		}
	}
}