C#: Improve BMN feed checking & handling.

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DotNet.cs

@@ -95,9 +95,9 @@ private string GetRestoreArgs(RestoreSettings restoreSettings)
                 args += " /p:EnableWindowsTargeting=true";
             }
 
-            if (restoreSettings.ExtraArgs is not null)
+            if (restoreSettings.NugetSources is not null)
             {
-                args += $" {restoreSettings.ExtraArgs}";
+                args += $" {restoreSettings.NugetSources}";
             }
 
             return args;

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/IDotNet.cs

@@ -17,7 +17,7 @@ public interface IDotNet
         IList<string> GetNugetFeedsFromFolder(string folderPath);
     }
 
-    public record class RestoreSettings(string File, string PackageDirectory, bool ForceDotnetRefAssemblyFetching, string? ExtraArgs = null, string? PathToNugetConfig = null, bool ForceReevaluation = false, bool TargetWindows = false);
+    public record class RestoreSettings(string File, string PackageDirectory, bool ForceDotnetRefAssemblyFetching, string? NugetSources = null, string? PathToNugetConfig = null, bool ForceReevaluation = false, bool TargetWindows = false);
 
     public partial record class RestoreResult(bool Success, IList<string> Output)
     {

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/NugetExeWrapper.cs

@@ -33,7 +33,7 @@ internal class NugetExeWrapper : IDisposable
         /// <summary>
         /// Create the package manager for a specified source tree.
         /// </summary>
-        public NugetExeWrapper(FileProvider fileProvider, DependencyDirectory packageDirectory, Semmle.Util.Logging.ILogger logger)
+        public NugetExeWrapper(FileProvider fileProvider, DependencyDirectory packageDirectory, Semmle.Util.Logging.ILogger logger, Func<bool> useDefaultFeed)
         {
             this.fileProvider = fileProvider;
             this.packageDirectory = packageDirectory;
@@ -43,7 +43,7 @@ public NugetExeWrapper(FileProvider fileProvider, DependencyDirectory packageDir
             {
                 logger.LogInfo($"Found packages.config files, trying to use nuget.exe for package restore");
                 nugetExe = ResolveNugetExe();
-                if (HasNoPackageSource())
+                if (HasNoPackageSource() && useDefaultFeed())
                 {
                     // We only modify or add a top level nuget.config file
                     nugetConfigPath = Path.Combine(fileProvider.SourceDir.FullName, "nuget.config");