Handle Azure folder creation

- Azure Blobs don't handle folders, have to create a fake "hidden" file entry to simulate the folder exists

--HG--
branch : dev

src/Orchard.Azure.Tests/FileSystems/Media/AzureBlobStorageProviderTests.cs

@@ -88,7 +88,6 @@ namespace Orchard.Azure.Tests.FileSystems.Media {
         [Test]
         [ExpectedException(typeof(ArgumentException))]
         public void CreateFolderThatExistsShouldThrow() {
-            // sebros: In Azure, the folder concept is just about checking files prefix. So until a file exists, a folder is nothing
             _azureBlobStorageProvider.CreateFile("folder/foo.txt");
             _azureBlobStorageProvider.CreateFolder("folder");
         }

src/Orchard.Azure/AzureFileSystem.cs

@@ -8,7 +8,10 @@ using Microsoft.WindowsAzure.StorageClient;
 using Orchard.FileSystems.Media;
 
 namespace Orchard.Azure {
-    public class AzureFileSystem {
+    public class AzureFileSystem
+    {
+        private const string FolderEntry = "$$$ORCHARD$$$.$$$";
+
         public string ContainerName { get; protected set; }
 
         private readonly CloudStorageAccount _storageAccount;
@@ -79,6 +82,10 @@ namespace Orchard.Azure {
             {
                 foreach (var blobItem in BlobClient.ListBlobsWithPrefix(prefix).OfType<CloudBlockBlob>())
                 {
+                    // ignore directory entries
+                    if(blobItem.Uri.AbsoluteUri.EndsWith(FolderEntry))
+                        continue;
+
                     yield return new AzureBlobFileStorage(blobItem);
                 }
             }
@@ -117,7 +124,9 @@ namespace Orchard.Azure {
             using (new HttpContextWeaver())
             {
                 Container.EnsureDirectoryDoesNotExist(path);
-                Container.GetDirectoryReference(path);
+
+                // Creating a virtually hidden file to make the directory an existing concept
+                CreateFile(path + "/" + FolderEntry);
             }
         }