Add PosixSymlinkFactory

src/Tgstation.Server.Host/Core/Application.cs

@@ -158,6 +158,7 @@ namespace Tgstation.Server.Host.Core
 			else
 			{
 				services.AddSingleton<ISystemIdentityFactory, PosixSystemIdentityFactory>();
+				services.AddSingleton<ISymlinkFactory, PosixSymlinkFactory>();
 			}
 
 			services.AddSingleton<IExecutor, Executor>();

src/Tgstation.Server.Host/IO/PosixSymlinkFactory.cs

@@ -0,0 +1,27 @@
+using Mono.Unix;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Tgstation.Server.Host.IO
+{
+	/// <summary>
+	/// <see cref="ISymlinkFactory"/> for posix systems
+	/// </summary>
+	sealed class PosixSymlinkFactory : ISymlinkFactory
+	{
+		/// <inheritdoc />
+		public Task CreateSymbolicLink(string targetPath, string linkPath, CancellationToken cancellationToken) => Task.Factory.StartNew(() =>
+		{
+			UnixFileSystemInfo fsInfo;
+			var isFile = File.Exists(targetPath);
+			cancellationToken.ThrowIfCancellationRequested();
+			if (isFile)
+				fsInfo = new UnixFileInfo(targetPath);
+			else
+				fsInfo = new UnixDirectoryInfo(targetPath);
+			cancellationToken.ThrowIfCancellationRequested();
+			fsInfo.CreateSymbolicLink(linkPath);
+		}, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current);
+	}
+}

src/Tgstation.Server.Host/IO/WindowsSymlinkFactory.cs

@@ -18,6 +18,7 @@ namespace Tgstation.Server.Host.IO
 			var flags = File.Exists(targetPath) ? 0 : 1; //SYMBOLIC_LINK_FLAG_DIRECTORY
 			flags |= 2; //SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE on win10 1607+
 
+			cancellationToken.ThrowIfCancellationRequested();
 			if (!NativeMethods.CreateSymbolicLink(linkPath, targetPath, flags))
 				throw new Win32Exception(Marshal.GetLastWin32Error());
 		}, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current);