Here is the way to install latest Subversion 1.7.x from WanDisco repository on Debian:
wget -q -O - http://opensource.wandisco.com/wandisco-debian.gpg | sudo apt-key add - echo "deb http://opensource.wandisco.com/debian/ squeeze svn17" > /etc/apt/sources.list.d/wandisco-subversion.list apt-get update apt-get install subversion subversion-tools