Do not use LibGit2SharpException overload for unknown message

Author: zentron

LibGit2Sharp/Core/Ensure.cs

@@ -148,7 +148,7 @@ private static unsafe void HandleError(int result)
             Func<string, GitErrorCategory, LibGit2SharpException> exceptionBuilder;
             if (!GitErrorsToLibGit2SharpExceptions.TryGetValue((GitErrorCode)result, out exceptionBuilder))
             {
-                exceptionBuilder = (m, c) => new LibGit2SharpException(m, c);
+                exceptionBuilder = (m, c) => new LibGit2SharpException($"{m}{(c == GitErrorCategory.Unknown ? string.Empty: $"\nGitErrorCode{c}")}");
             }
 
             throw exceptionBuilder(errorMessage, errorCategory);