Author: Dongsheng Cai
MDL-24410, repository upload plugin allows rename file
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0bd269b7a2436205497bc2afcdd86d2ec0ae2f41
http://github.com/moodle/moodle/commit/0bd269b7a2436205497bc2afcdd86d2ec0ae2f41
+ 2.0 en [fileexists,core_repository]