This is item #1 from Greg Hudson's mail about 2.0 API improvements:
http://subversion.tigris.org/servlets/ReadMsg?list=dev&msgNo=67095
"Callbacks should always have pool arguments. Otherwise we wind up creating and
destroying subpools in the callbacks, which is anachronistic and less efficient
than the usual iteration-pool approach. Specific places I have noticed lack of
callbacks include the svn_stream callbacks and svn_txdelta_window_handler_t."
In a reply, Mike Pilato added:
"Also, all callbacks should return svn_error_t's."
Task
Major