anchor.diff:  -check_permissions([{traverse_ancestors, 2}, {traverse_ancestors, {path, 3}}, {?delete, 2}]).
   rename(CTX, SourceEntry, TargetPath) ->
       ?debug("Renaming file ~p to ~p...", [SourceEntry, TargetPath]),
  -    case file_meta:exists({path, TargetPath}) of
  -        true ->
  -            #fuse_response{status = #status{code = ?EEXIST}};
  -        false ->
  -            case file_meta:get(SourceEntry) of
  -                {ok, #document{value = #file_meta{type = ?DIRECTORY_TYPE}} = FileDoc} ->
  -                    rename_dir(CTX, FileDoc, TargetPath);
  -                {ok, FileDoc} ->
  -                    rename_file(CTX, FileDoc, TargetPath)
  -            end
  +    case file_meta:get(SourceEntry) of
  +        {ok, #document{value = #file_meta{type = ?DIRECTORY_TYPE}} = FileDoc} ->
  +            rename_dir(CTX, FileDoc, TargetPath);
  +        {ok, FileDoc} ->
  +            rename_file(CTX, FileDoc, TargetPath)
       end.
   
   %%--------------------------------------------------------------------
  
positive.code:         true ->
              #fuse_response{status = #status{code = ?EINVAL}};
          false ->
              rename_impl(CTX, SourceEntry, TargetPath)
      end.
  
  %%--------------------------------------------------------------------
  
negative.code:     #fuse_response{} | no_return().
  -check_permissions([{?delete_object, {parent, 2}}, {?add_object, {parent, {path, 3}}}]).
  rename_file(CTX, SourceEntry, TargetPath) ->
      case file_meta:get({path, TargetPath}) of
          {ok, #document{value = #file_meta{type = ?DIRECTORY_TYPE}}} ->
              #fuse_response{status = #status{code = ?EISDIR}};
          {ok, TargetDoc} ->
              case delete_impl(CTX, TargetDoc) of
                  #fuse_response{status = #status{code = ?OK}} ->
                      rename_impl(CTX, SourceEntry, TargetPath);
                  NotOK ->
                      NotOK
              end
      end.
  
  %%--------------------------------------------------------------------
  %% @doc Renames file_meta doc.
  