anchor.diff:      od_share:share_guid().
   uuid_to_share_guid(FileUuid, SpaceId, undefined) ->
       uuid_to_guid(FileUuid, SpaceId);
  -uuid_to_share_guid(FileUuid, undefined, ShareId) ->
  -    <<?SHARE_GUID_PREFIX, ?GUID_SEPARATOR, FileUuid/binary,
  -        ?GUID_SEPARATOR,
  -        ?GUID_SEPARATOR, ShareId/binary
  -    >>;
   uuid_to_share_guid(FileUuid, SpaceId, ShareId) ->
  +    DefinedSpaceId = utils:ensure_defined(SpaceId, undefined, <<>>),
       <<?SHARE_GUID_PREFIX, ?GUID_SEPARATOR,  FileUuid/binary,
  -        ?GUID_SEPARATOR, SpaceId/binary,
  +        ?GUID_SEPARATOR, DefinedSpaceId/binary,
           ?GUID_SEPARATOR, ShareId/binary
       >>.
   
  
positive.code: -spec unpack_guid(FileGuid :: fslogic_worker:file_guid()) ->
      {file_meta:uuid(), od_space:id() | undefined}.
  unpack_guid(FileGuid) ->
      try binary:split(FileGuid, <<"#">>, [global]) of
          [<<?SHARE_GUID_PREFIX>>, FileUuid, <<>>, _ShareId] ->
              {FileUuid, undefined};
          [<<?SHARE_GUID_PREFIX>>, FileUuid, SpaceId, _ShareId] ->
              {FileUuid, SpaceId};
          [<<?GUID_PREFIX>>, FileUuid, <<>>] ->
              {FileUuid, undefined};
          [<<?GUID_PREFIX>>, FileUuid, SpaceId] ->
              {FileUuid, SpaceId};
          _ ->
              {FileGuid, undefined}
      catch
          _:_ ->
              {FileGuid, undefined}
      end.
  
  %%--------------------------------------------------------------------
  %% @private
  
negative.code:     {file_meta:uuid(), undefined | od_space:id(), od_share:id() | undefined}.
  unpack_share_guid(ShareGuid) ->
      try binary:split(ShareGuid, <<?GUID_SEPARATOR>>, [global]) of
          [<<?SHARE_GUID_PREFIX>>, FileUuid, SpaceId, ShareId] ->
              NonEmptySpaceId = utils:ensure_defined(SpaceId, <<>>, undefined),
              {FileUuid, NonEmptySpaceId, ShareId};
          [<<?GUID_PREFIX>>, FileUuid, SpaceId] ->
              NonEmptySpaceId = utils:ensure_defined(SpaceId, <<>>, undefined),
              {FileUuid, NonEmptySpaceId, undefined};
          _ ->
              {ShareGuid, undefined, undefined}
      catch
  