Make 'svn diff --old=FOO --new=BAR' default to WORKING revision rather than
BASE for the old target if the new target is explicitly specified, so that
it is the reverse of the diff from 'svn diff --old=BAR --new=FOO'.

Patch by: Alexey Neyman <stilor{_AT_}att.net>

* subversion/svn/diff-cmd.c
  (svn_cl__diff): Change defaults as described and simplify the logic.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1443821 13f79535-47bb-0310-9956-ffa450edef68