Exception: "An item with the same key has already been added" when comparing commits

I get ArgumentException when comparing two commits from https://github.com/shageman/the_next_big_thing with v.0.23.1.0

 System.ArgumentException:`  An item with the same key has already been added.
   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
   at LibGit2Sharp.Patch.AddFileChange(git_diff_delta* delta) in c:\Git\LibGit2Sharp-2\LibGit2Sharp\Patch.cs:line 54
   at LibGit2Sharp.Patch..ctor(DiffHandle diff) in c:\Git\LibGit2Sharp-2\LibGit2Sharp\Patch.cs:line 43
   at LibGit2Sharp.Diff.<.cctor>b__1b(DiffHandle diff) in c:\Git\LibGit2Sharp-2\LibGit2Sharp\Diff.cs:line 104
   at LibGit2Sharp.Diff.BuildDiffResult[T](DiffHandle diff) in c:\Git\LibGit2Sharp-2\LibGit2Sharp\Diff.cs:line 120
   at LibGit2Sharp.Diff.Compare[T](Tree oldTree, Tree newTree, IEnumerable`1 paths, ExplicitPathsOptions explicitPathsOptions, CompareOptions compareOptions) in c:\Git\LibGit2Sharp-2\LibGit2Sharp\Diff.cs:line 253
   at LibGit2Sharp.Diff.Compare[T](Tree oldTree, Tree newTree) in c:\Git\LibGit2Sharp-2\LibGit2Sharp\Diff.cs:line 157

The code I'am using:
this.repository.Diff.Compare<Patch>(commitB.Tree, commitA.Tree);

commitA: a9a82df96ab1f73c69b2668b91eda31e672bbf98 Move rails application back to root to make heroku deployment work again
commitB: ede0b0c359d5af516889563bebafd51b7f43115a Gemnasium doesn't recognize Gemfile when its not in the root. Let's try symlinks

Beginne mit LibGit2Sharp/Patch.cs bei AddFileChange und überprüfe den Aufrufpfad von Diff.cs während Diff.Compare. Reproduziere den Vergleich mit den Commits a9a82df96ab1f73c69b2668b91eda31e672bbf98 und ede0b0c359d5af516889563bebafd51b7f43115a. Erledigt ist die Aufgabe, wenn dieser Vergleich nicht mehr die ArgumentException wegen doppelter Schlüssel auslöst und die erwarteten Patch-Änderungen zurückgibt.