我试过：
sudo apt-get install subversion
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package subversion is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'subversion' has no installation candidate
我需要一个命令行版本来支持在 Ubuntu 14.xx 下开发并使用svn.