To update SVN on MacOS 10.10 you need to first uninstall old version. You can do that just by deleting the binary.
Type in console:
Then remove it
sudo rm /usr/bin/svn
Use then Homebrew to install new version.
brew install svn
It takes few minutes to install.
I also had to link SVN again on homebrew (maybe i had some old references)
brew link --overwrite subversion
… and it’s done.