Replaced call to Directory.Delete() with a recursive method which properly...

Replaced call to Directory.Delete() with a recursive method which properly deal with read-only attributes.

libgit2sharp.Tests/ReadWriteRepositoryFixtureBase.cs

@@ -30,7 +30,7 @@ public void Setup()
         [TestFixtureTearDown]
         public void TestFixtureTearDown()
         {
-            Directory.Delete(_testRepositoriesDirectoryPath, true);
+            DeleteDirectory(_testRepositoriesDirectoryPath);
         }
 
         public static void CopyFilesRecursively(DirectoryInfo source, DirectoryInfo target)
@@ -57,5 +57,27 @@ static private string RetrieveAssemblyDirectory()
             string path = Uri.UnescapeDataString(uri.Path);
             return Path.GetDirectoryName(path);
         }
+
+        private static void DeleteDirectory(string directoryPath)
+        {
+            // From http://stackoverflow.com/questions/329355/cannot-delete-directory-with-directory-deletepath-true/329502#329502
+
+            string[] files = Directory.GetFiles(directoryPath);
+            string[] dirs = Directory.GetDirectories(directoryPath);
+
+            foreach (string file in files)
+            {
+                File.SetAttributes(file, FileAttributes.Normal);
+                File.Delete(file);
+            }
+
+            foreach (string dir in dirs)
+            {
+                DeleteDirectory(dir);
+            }
+
+            File.SetAttributes(directoryPath, FileAttributes.Normal);
+            Directory.Delete(directoryPath, false);
+        }
     }
 }
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