Fix OD build paths being too long on Windows

src/Tgstation.Server.Host/Components/Engine/OpenDreamInstaller.cs

@@ -206,21 +206,25 @@ namespace Tgstation.Server.Host.Components.Engine
 
 			var dotnetPath = dotnetPaths[selectedPathIndex];
 
-			await using (var buildProcess = ProcessExecutor.LaunchProcess(
-				dotnetPath,
+			int? buildExitCode = null;
+			await HandleExtremelyLongPathOperation(
+				async shortenedPath =>
+				{
+					await using var buildProcess = ProcessExecutor.LaunchProcess(
+						dotnetPath,
+						shortenedPath,
+						"build -c Release /p:TgsEngineBuild=true",
+						null,
+						true,
+						true);
+					buildExitCode = await buildProcess.Lifetime;
+					Logger.LogDebug("Build output:{newLine}{output}", Environment.NewLine, await buildProcess.GetCombinedOutput(cancellationToken));
+				},
 				sourcePath,
-				"build -c Release /p:TgsEngineBuild=true",
-				null,
-				true,
-				true))
-			{
-				var buildExitCode = await buildProcess.Lifetime;
+				cancellationToken);
 
-				Logger.LogDebug("Build output:{newLine}{output}", Environment.NewLine, await buildProcess.GetCombinedOutput(cancellationToken));
-
-				if (buildExitCode != 0)
-					throw new JobException("OpenDream build failed!");
-			}
+			if (buildExitCode != 0)
+				throw new JobException("OpenDream build failed!");
 
 			await IOManager.MoveDirectory(
 				IOManager.ConcatPath(
@@ -250,6 +254,19 @@ namespace Tgstation.Server.Host.Components.Engine
 			return ValueTask.CompletedTask;
 		}
 
+		/// <summary>
+		/// Perform an operation on a very long path.
+		/// </summary>
+		/// <param name="shortenedPathOperation">A <see cref="Func{T, TResult}"/> taking a shortened path and resulting in a <see cref="ValueTask"/> representing the running operation.</param>
+		/// <param name="originalPath">The original path to the directory.</param>
+		/// <param name="cancellationToken">The <see cref="CancellationToken"/> for the operation.</param>
+		/// <returns>A <see cref="ValueTask"/> representing the running operation.</returns>
+		protected virtual ValueTask HandleExtremelyLongPathOperation(
+			Func<string, ValueTask> shortenedPathOperation,
+			string originalPath,
+			CancellationToken cancellationToken)
+			=> shortenedPathOperation(originalPath); // based god linux has no such weakness
+
 		/// <summary>
 		/// Gets the paths to the server and client executables.
 		/// </summary>

src/Tgstation.Server.Host/Components/Engine/WindowsOpenDreamInstaller.cs

@@ -21,6 +21,11 @@ namespace Tgstation.Server.Host.Components.Engine
 	/// </summary>
 	sealed class WindowsOpenDreamInstaller : OpenDreamInstaller
 	{
+		/// <summary>
+		/// The <see cref="ISymlinkFactory"/> for the <see cref="WindowsOpenDreamInstaller"/>.
+		/// </summary>
+		readonly ISymlinkFactory symlinkFactory;
+
 		/// <summary>
 		/// Initializes a new instance of the <see cref="WindowsOpenDreamInstaller"/> class.
 		/// </summary>
@@ -30,13 +35,15 @@ namespace Tgstation.Server.Host.Components.Engine
 		/// <param name="processExecutor">The <see cref="IProcessExecutor"/> for the <see cref="OpenDreamInstaller"/>.</param>
 		/// <param name="repositoryManager">The <see cref="IRepositoryManager"/> for the <see cref="OpenDreamInstaller"/>.</param>
 		/// <param name="generalConfigurationOptions">The <see cref="IOptions{TOptions}"/> of <see cref="GeneralConfiguration"/> for the <see cref="OpenDreamInstaller"/>.</param>
+		/// <param name="symlinkFactory">The value of <see cref="symlinkFactory"/>.</param>
 		public WindowsOpenDreamInstaller(
 			IIOManager ioManager,
 			ILogger<WindowsOpenDreamInstaller> logger,
 			IPlatformIdentifier platformIdentifier,
 			IProcessExecutor processExecutor,
 			IRepositoryManager repositoryManager,
-			IOptions<GeneralConfiguration> generalConfigurationOptions)
+			IOptions<GeneralConfiguration> generalConfigurationOptions,
+			ISymlinkFactory symlinkFactory)
 			: base(
 				ioManager,
 				logger,
@@ -45,6 +52,7 @@ namespace Tgstation.Server.Host.Components.Engine
 				repositoryManager,
 				generalConfigurationOptions)
 		{
+			this.symlinkFactory = symlinkFactory ?? throw new ArgumentNullException(nameof(symlinkFactory));
 		}
 
 		/// <inheritdoc />
@@ -59,6 +67,21 @@ namespace Tgstation.Server.Host.Components.Engine
 					installPath,
 					cancellationToken));
 
+		/// <inheritdoc />
+		protected override async ValueTask HandleExtremelyLongPathOperation(Func<string, ValueTask> shortenedPathOperation, string originalPath, CancellationToken cancellationToken)
+		{
+			var shortPath = $"C:/{Guid.NewGuid()}";
+			await symlinkFactory.CreateSymbolicLink(originalPath, shortPath, cancellationToken);
+			try
+			{
+				await shortenedPathOperation(shortPath);
+			}
+			finally
+			{
+				await IOManager.DeleteDirectory(shortPath, CancellationToken.None); // DCT: Should always run.
+			}
+		}
+
 		/// <summary>
 		/// Attempt to add the DreamDaemon executable as an exception to the Windows firewall.
 		/// </summary>