比较版本内容差异的时候，遭遇到错误：Unreadable path encountered; access denied;

解决方法：编辑[代码仓库目录下]/conf/svnserve.conf
1. 将[anon-access]的值设置为[none]。如下：
[general]
### These options control access to the repository for unauthenticated
### and authenticated users.  Valid values are "write", "read",
### and "none".  The sample settings below are the defaults.
# anon-access = read
anon-access = none
2. 重启SVN服务了。
killall -HUP svnserve
svnserve -d -r /home/repository # [/home/repository]就是你的仓库跟目录