我正在一台全新的 Mac 上安装一些 Homebrew 软件包。但是，链接时出现一些错误：
ln: ./libsvn_wc-1.dylib: Permission denied
Error: The linking step did not complete successfully
The package built, but is not symlinked into /usr/local
You can try again using `brew link subversion'
Error: Could not create symlink /usr/local/lib/libsvn_wc-1.dylib.
Check that you have permssions on /usr/local/lib
==> Summary
/usr/local/Cellar/subversion/1.6.15: 88 files, 6.0M, built in 38 seconds
所以 SVN 并没有真正正确安装，正如我们在这里看到的：
charon:~ werner$ which svn
/usr/bin/svn
Git 的相同错误：
charon:~ werner$ brew link git
Error: Permission denied - /usr/local/lib/python2.6
但是，这个安装正确：
charon:~ werner$ …