Fix issue #2531: Added a warning message when 'svn switch --relocate' doesn't result in any changes. * subversion/libsvn_wc/relocate.c (relocate_entry): Add a touched parameter. Add a check to set touched to true if the entry is actually relocated. (svn_wc_relocate2): Extract out all of the contents of svn_wc_relocate2 and moved it into the new perform_relocate function. Add code to initialize touched, call perform_relocate, and then throw a warning if touched returns as false. (perform_relocate): New function, created from the former contents of svn_wc_relocate2. Add a touched parameter, to be passed through to all calls to relocate_entry. * subversion/tests/cmdline/switch_tests.py (relocate_with_bad_url): New test case to exercise relocation without a valid FROM url.