Always read from physical index on RetrieveStatus()

Fixes #322

Author: dahlbyk

LibGit2Sharp.Tests/IndexFixture.cs

@@ -242,5 +242,37 @@ public void CanReadIndexEntryAttributes()
                 Assert.Equal(Mode.ExecutableFile, repo.Index["1/branch_file.txt"].Mode);
             }
         }
+
+        [Fact]
+        public void CanCopeWithExternalChangesToTheIndex()
+        {
+            SelfCleaningDirectory scd = BuildSelfCleaningDirectory();
+
+            Touch(scd.DirectoryPath, "a.txt", "a\n");
+            Touch(scd.DirectoryPath, "b.txt", "b\n");
+
+            using (var repoWrite = Repository.Init(scd.DirectoryPath))
+            using (var repoRead = new Repository(scd.DirectoryPath))
+            {
+                var writeStatus = repoWrite.Index.RetrieveStatus();
+                Assert.True(writeStatus.IsDirty);
+                Assert.Equal(0, repoWrite.Index.Count);
+
+                var readStatus = repoRead.Index.RetrieveStatus();
+                Assert.True(readStatus.IsDirty);
+                Assert.Equal(0, repoRead.Index.Count);
+
+                repoWrite.Index.Stage("*");
+                repoWrite.Commit("message", DummySignature);
+
+                writeStatus = repoWrite.Index.RetrieveStatus();
+                Assert.False(writeStatus.IsDirty);
+                Assert.Equal(2, repoWrite.Index.Count);
+
+                readStatus = repoRead.Index.RetrieveStatus();
+                Assert.False(readStatus.IsDirty);
+                Assert.Equal(2, repoRead.Index.Count);
+            }
+        }
     }
 }

LibGit2Sharp/Core/NativeMethods.cs

@@ -490,6 +490,14 @@ internal static extern int git_index_open(
             out IndexSafeHandle index,
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(FilePathMarshaler))] FilePath indexpath);
 
+        [DllImport(libgit2)]
+        internal static extern int git_index_read(IndexSafeHandle index);
+
+        [DllImport(libgit2)]
+        internal static extern int git_index_read_tree(
+            IndexSafeHandle index,
+            GitObjectSafeHandle tree);
+
         [DllImport(libgit2)]
         internal static extern int git_index_remove_bypath(
             IndexSafeHandle index,

LibGit2Sharp/Core/Proxy.cs

@@ -771,6 +771,25 @@ public static IndexSafeHandle git_index_open(FilePath indexpath)
             }
         }
 
+        public static void git_index_read(IndexSafeHandle index)
+        {
+            using (ThreadAffinity())
+            {
+                int res = NativeMethods.git_index_read(index);
+                Ensure.ZeroResult(res);
+            }
+        }
+
+        public static void git_index_read_tree(IndexSafeHandle index, Repository repo, Tree tree)
+        {
+            using (ThreadAffinity())
+            using (var treePtr = new ObjectSafeWrapper(tree.Id, repo.Handle))
+            {
+                int res = NativeMethods.git_index_read_tree(index, treePtr.ObjectPtr);
+                Ensure.ZeroResult(res);
+            }
+        }
+
         public static void git_index_remove_bypath(IndexSafeHandle index, FilePath path)
         {
             using (ThreadAffinity())

LibGit2Sharp/Index.cs

@@ -477,6 +477,16 @@ private string RemoveFromIndex(string relativePath)
             return relativePath;
         }
 
+        private void UpdateFromPhysicalIndex()
+        {
+            Proxy.git_index_read(handle);
+            var tip = repo.Head.Tip;
+            if (tip != null)
+            {
+                Proxy.git_index_read_tree(handle, repo, tip.Tree);
+            }
+        }
+
         private void UpdatePhysicalIndex()
         {
             Proxy.git_index_write(handle);
@@ -502,6 +512,7 @@ public virtual FileStatus RetrieveStatus(string filePath)
         /// <returns>A <see cref = "RepositoryStatus" /> holding the state of all the files.</returns>
         public virtual RepositoryStatus RetrieveStatus()
         {
+            UpdateFromPhysicalIndex();
             return new RepositoryStatus(repo);
         }