C#: Allow specifying package feeds for dotnet restore as command line arguments

Author: mbg

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

@@ -67,6 +67,16 @@ private string GetRestoreArgs(RestoreSettings restoreSettings)
                 args += $" --configfile \"{restoreSettings.PathToNugetConfig}\"";
             }
 
+            // Add package sources. If any are present, they override all sources specified in
+            // the configuration file(s).
+            if (restoreSettings.Sources != null)
+            {
+                foreach (string source in restoreSettings.Sources)
+                {
+                    args += $" -s {source}";
+                }
+            }
+
             if (restoreSettings.ForceReevaluation)
             {
                 args += " --force";

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? PathToNugetConfig = null, bool ForceReevaluation = false, bool TargetWindows = false);
+    public record class RestoreSettings(string File, string PackageDirectory, bool ForceDotnetRefAssemblyFetching, IList<string>? Sources = null, string? PathToNugetConfig = null, bool ForceReevaluation = false, bool TargetWindows = false);
 
     public partial record class RestoreResult(bool Success, IList<string> Output)
     {