从github上下载一个项目的子目录

https://github.com/pbojinov/developer.chrome.com/tree/master/extensions/examples/extensions/proxy_configuration
https://github.com/pbojinov/developer.chrome.com/trunk/extensions/examples/extensions/proxy_configuration

将 “tree/master”替换成 “trunk”，这样git地址就变成了一个svn地址，再用svn导出便可。 [1]