dotjosh
diff --git a/‎LibGit2Sharp.Tests/IndexFixture.cs
Lines changed: 39 additions & 1 deletion b/‎LibGit2Sharp.Tests/IndexFixture.cs
Lines changed: 39 additions & 1 deletion
diff --git a/‎LibGit2Sharp/Index.cs
Lines changed: 14 additions & 0 deletions b/‎LibGit2Sharp/Index.cs
Lines changed: 14 additions & 0 deletions
@@ -63,7 +63,7 @@ public void CanEnumeratorStagedFiles()
         }
 
         [Test]
-        public void CanReadIndexEntry()
+        public void CanFetchAnIndexEntryByItsName()
         {
             using (var repo = new Repository(Constants.StandardTestRepoPath))
             {
@@ -99,6 +99,7 @@ public void CanStageANewFile()
             {
                 var count = repo.Index.Count;
                 const string filename = "unit_test.txt";
+                repo.Index[filename].ShouldBeNull();
                 File.WriteAllText(Path.Combine(repo.Info.WorkingDirectory, filename), "some contents");
 
                 repo.Index.Stage(filename);
@@ -108,6 +109,43 @@ public void CanStageANewFile()
             }
         }
 
+        [Test]
+        public void StagingANewVersionOfAFileThenUnstagingRevertsTheBlobToTheVersionOfHead()
+        {
+            using (var scd = new SelfCleaningDirectory())
+            {
+                string dir = Repository.Init(scd.DirectoryPath);
+
+                using (var repo = new Repository(dir))
+                {
+                    repo.Index.Count.ShouldEqual(0);
+
+                    const string fileName = "myFile.txt";
+
+                    var fullpath = Path.Combine(repo.Info.WorkingDirectory, fileName);
+                    
+                    const string initialContent = "Hello?";
+                    File.AppendAllText(fullpath, initialContent);
+                    
+                    repo.Index.Stage(fileName);
+                    var blobId = repo.Index[fileName].Id;
+
+                    repo.Commit(Constants.Signature, Constants.Signature, "Initial commit");
+                    repo.Index.Count.ShouldEqual(1);
+
+                    File.AppendAllText(fullpath, "Is there there anybody out there?");
+                    repo.Index.Stage(fileName);
+
+                    repo.Index.Count.ShouldEqual(1);
+                    repo.Index[fileName].Id.ShouldNotEqual((blobId));
+
+                    repo.Index.Unstage(fileName);
+                    repo.Index.Count.ShouldEqual(1);
+                    repo.Index[fileName].Id.ShouldEqual((blobId));
+                }
+            }
+        }
+
         [Test]
         public void CanStageANewFileInAPersistentManner()
         {
 
@@ -140,6 +140,8 @@ public void Unstage(string path)
 
             RemoveFromIndex(relativePath);
 
+            RestorePotentialPreviousVersionOf(relativePath);
+
             UpdatePhysicalIndex();
         }
 
@@ -181,6 +183,18 @@ private void RemoveFromIndex(string relativePath)
             Ensure.Success(res);
         }
 
+        private void RestorePotentialPreviousVersionOf(string relativePath)
+        {
+            var currentHeadBlob = repo.Head.Tip.Tree[relativePath];
+            if ((currentHeadBlob == null) || currentHeadBlob.Type != GitObjectType.Blob)
+            {
+                return;
+            }
+            
+            File.WriteAllBytes(Path.Combine(repo.Info.WorkingDirectory, relativePath), ((Blob) currentHeadBlob.Target).Content);
+            AddToIndex(relativePath);
+        }
+
         private void UpdatePhysicalIndex()
         {
             int res = NativeMethods.git_index_write(handle);