SVN的branch和tag管理都是通过copy实现的，它并没有独立的branche和tag概念，它仅仅是管理文件的历史，trunk、branch、tag对于SVN而言都是普通的文件夹
创建分支：
svn copy http://svn.example.com/repos/calc/trunk \
http://svn.example.com/repos/calc/branches/my-calc-branch \
-m "Creating a private branch of /calc/trunk."
创建Tag：
svn copy http://svn.example.com/repos/calc/trunk \
http://svn.example.com/repos/calc/tags/release-1.0 \
-m "Tagging the 1.0 release of the 'calc' project."