Silently ignore rewriting of commits under refs/notes/*

Fix #942

Author: nulltoken

LibGit2Sharp.Tests/FilterBranchFixture.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using LibGit2Sharp.Tests.TestHelpers;
@@ -801,6 +802,26 @@ public void HandlesNameRewritingOfChainedTags()
             Assert.Equal(annotationB, backedUpTag.ResolveToDirectReference().Target);
         }
 
+        [Fact]
+        public void RewritingNotesHasNoEffect()
+        {
+            var notesRefsRetriever = new Func<IEnumerable<Reference>>(() => repo.Refs.Where(r => r.CanonicalName.StartsWith("refs/notes/")));
+            var originalNotesRefs = notesRefsRetriever().ToList();
+            var commits = repo.Commits.QueryBy(new CommitFilter { Since = originalNotesRefs }).ToArray();
+
+            repo.Refs.RewriteHistory(new RewriteHistoryOptions
+            {
+                OnError = OnError,
+                OnSucceeding = OnSucceeding,
+                CommitHeaderRewriter =
+                    c => CommitRewriteInfo.From(c, author: Constants.Signature),
+            }, commits);
+
+            AssertSucceedingButNotError();
+
+            Assert.Equal(originalNotesRefs.OrderBy(r => r.CanonicalName), notesRefsRetriever().OrderBy(r => r.CanonicalName));
+        }
+
         private static string TagNameRewriter(string name, bool isAnnotated, string target)
         {
             const string tagPrefix = "refs/tags/";

LibGit2Sharp/Core/HistoryRewriter.cs

@@ -59,7 +59,11 @@ public void Execute()
                 // before A.
                 foreach (var reference in refsToRewrite.OrderBy(ReferenceDepth))
                 {
-                    // TODO: Check how rewriting of notes actually behaves
+                    // TODO: Rewrite refs/notes/* properly
+                    if (reference.CanonicalName.StartsWith("refs/notes/"))
+                    {
+                        continue;
+                    }
 
                     RewriteReference(reference);
                 }