Where is SVN on OS X Mountain Lion?
Solution 1:
Install the latest Xcode from the Mac App Store.
Go to Xcode » Preferences » Downloads » Command Line Tools » Install.
If you don't want to download/install Xcode, you can always just download Command Line Tools for Mountain Lion from Developer Downloads.
Solution 2:
If you have Xcode installed and if you use bash :
$> vi ~/.profile
add this at the end of your .profile PATH="${PATH}:/Applications/Xcode.app/Contents/Developer/usr/bin/"
$> source ~/.profile
It should be working