Fix issue #1313: Copying between two different repositories gave an incomprehensible error message.
Fix issue #1313: Copying between two different repositories gave an
incomprehensible error message.

* subversion/libsvn_client/copy.c
  (repos_to_repos_copy): Detect the condition and produce a better
    error message.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@846778 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion