anchor.diff:  %%--------------------------------------------------------------------
   -spec request_synchronization(user_ctx:ctx(), file_ctx:ctx(), block(),
       Prefetch :: boolean(), transfer:id() | undefined, non_neg_integer()) ->
  -    {ok, #file_location_changed{}} | {error, Reason :: any()}.
  +    ok | {error, Reason :: any()}.
   request_synchronization(UserCtx, FileCtx, Block, Prefetch, TransferId, Priority) ->
       request_synchronization(UserCtx, FileCtx, Block, Prefetch, TransferId,
           Priority, async).
  
positive.code: %%--------------------------------------------------------------------
  -spec request_synchronization(user_ctx:ctx(), file_ctx:ctx(), block(),
      Prefetch :: boolean(), transfer:id() | undefined, non_neg_integer(),
      request_type()) -> {ok, #file_location_changed{}} | {error, Reason :: any()}.
  request_synchronization(UserCtx, FileCtx, Block, Prefetch, TransferId,
      Priority, SyncType) ->
      EnlargedBlock = enlarge_block(Block, Prefetch),
  
negative.code:         off ->
              false;
          _ ->
              ToInvalidate = [FinalBlock || {_From, FinalBlock, _Type} <- FinalBlocks],
              Blocks2 = fslogic_blocks:consolidate(fslogic_blocks:invalidate(Blocks, ToInvalidate)),
              lists:foreach(fun(Block) ->
                  flush_blocks_list([Block], ExcludeSessions, all)
  