benny-innofaith (in #svn IRC)

Found

r1779948

r1779948 | stsp | 2017-01-23 15:54:37 +0000 (Mon, 23 Jan 2017)

* subversion/libsvn_client/copy.c
  (verify_wc_dsts): Provide a better error message when a copy/move operation
   attempts to use an existing, but unversioned, target directory.

Found by: benny-innofaith (in #svn IRC)