because of a new branch, 'rc' is no longer unique

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@23473 71c3de6d-444a-0410-be80-ed276b4c234a

rc-merge.sh

 #!/bin/bash -ex
 # merge back the RC branch.
-svnmerge merge -S rc .
+svnmerge merge -S /branches/rc .
 svn commit -F svnmerge-commit-message.txt