Add nuget-config-dir parameter support.

src/assembly-differ/Program.cs

@@ -21,15 +21,17 @@ internal static class Program
 		private static SuggestedVersionChange _preventChange = SuggestedVersionChange.None;
 		private static bool _allowEmptyPreviousNuget = false;
 
+		private static readonly NuGetInstallerOptions _nugetInstallerOptions = new NuGetInstallerOptions();
+
 		private static HashSet<string> Targets { get; } = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
 
 		private static int Main(string[] args)
 		{
 			var providers = new AssemblyProviderFactoryCollection(
 				new AssemblyProviderFactory(),
 				new DirectoryAssemblyProviderFactory(),
-				new NuGetAssemblyProviderFactory(new Providers.NuGet.NuGet()),
-				new PreviousNuGetAssemblyProviderFactory(new PreviousNugetLocator()),
+				new NuGetAssemblyProviderFactory(new Providers.NuGet.NuGet(_nugetInstallerOptions)),
+				new PreviousNuGetAssemblyProviderFactory(new PreviousNugetLocator(_nugetInstallerOptions)),
 				new GitHubAssemblyProviderFactory(new Git(Environment.GetEnvironmentVariable("GIT")))
 			);
 
@@ -49,6 +51,8 @@ private static int Main(string[] args)
 					c => _preventChange = Enum.Parse<SuggestedVersionChange>(c, true)},
 				{"a|allow-empty-previous-nuget=", "",
 					n => _allowEmptyPreviousNuget = n != null},
+				{"c|nuget-config-dir=", "the search directory for NuGet to find a NuGet.config file. Defaults to `null` which will use the root config. Use only if using NuGet as a provider.",
+					c => SetNugetConfigSearchDirectory(c) },
 				{"h|?|help", "show this message and exit", h => _help = h != null},
 			};
 
@@ -165,6 +169,21 @@ private static void AddTarget(string input)
 				Targets.Add(part);
 		}
 
+		private static void SetNugetConfigSearchDirectory(string searchDirectory)
+		{
+			if (string.IsNullOrEmpty(searchDirectory))
+			{
+				throw new ArgumentException("Cannot be null or empty", nameof(searchDirectory));
+			}
+
+			if (!Directory.Exists(searchDirectory))
+			{
+				throw new DirectoryNotFoundException($"Could not find directory from supplied value of '{searchDirectory}'.");
+			}
+
+			_nugetInstallerOptions.NuGetConfigSearchDirectory = searchDirectory;
+		}
+
 		private static void ShowHelp(OptionSet options, AssemblyProviderFactoryCollection providerFactoryCollection)
 		{
 			Console.ForegroundColor = ConsoleColor.Green;

src/assembly-differ/Providers/NuGet/NuGet.cs

@@ -19,15 +19,25 @@ public interface INuGet
 		NuGetPackage InstallPackage(string packageName, string version, string targetDirectory);
 	}
 
+	public class NuGetInstallerOptions
+	{
+		public string NuGetConfigSearchDirectory { get; set; }
+	}
+
 	public class NuGet : INuGet
 	{
+		protected NuGetInstallerOptions Options { get; }
+
+		public NuGet(NuGetInstallerOptions options)
+			=> Options = options;
+
 		public virtual NuGetPackage InstallPackage(string packageName, string version, string targetDirectory)
 		{
 			if (!Directory.Exists(targetDirectory)) Directory.CreateDirectory(targetDirectory);
 
 			var packageVersion = NuGetVersion.Parse(version);
 			var nuGetFramework = NuGetFramework.AnyFramework;
-			var settings = Settings.LoadDefaultSettings(root: null);
+			var settings = Settings.LoadDefaultSettings(root: Options?.NuGetConfigSearchDirectory);
 			var sourceRepositoryProvider = new SourceRepositoryProvider(
 				new PackageSourceProvider(settings), Repository.Provider.GetCoreV3());
 

src/assembly-differ/Providers/PreviousNuget/PreviousNugetLocator.cs

@@ -13,6 +13,9 @@ namespace Differ.Providers.PreviousNuGet
 {
 	public class PreviousNugetLocator : Differ.Providers.NuGet.NuGet
 	{
+		public PreviousNugetLocator(NuGetInstallerOptions options) : base(options)
+		{}
+
 		public override NuGetPackage InstallPackage(string packageName, string currentVersion, string targetDirectory)
 		{
 			var nugetVersion = new NuGetVersion(currentVersion);