今天使用Android Studio比对代码的时候突然报错：
Error:svn: E155036: Please see the 'svn upgrade' command
svn: E155036: The working copy at ‘xxx/xxx' is too old (format 29) to work with client version '1.9.4 (r1740329)' (expects format 31). You need to upgrade the working copy first.
按照提示在Android Studio的terminal下输入：svn upgrade，然后得到如下报错：
svn: E155019: Can't upgrade ‘xxx/xxx/aaa' as it is not a working copy root
svn: E000002: Working copy database ‘xxx/xxx/aaa/.svn/wc.db' not found
svn: E200042: Additional errors:
svn: E000002: Can't open file ‘xxx/xxx/aaa/.svn/entries': No such file or directory
说是当前目录不是一个working copy的根目录，然后在当前目录下找不到.svn目录下的一些文件。于是到文件目录里面看了一下发现有一个与工程根目录同级的目录叫”.svn”，估计要升级的就是这个东东了。于是在Android Studio的terminal下输入：“cd ../”定位到上一级目录即”.svn”所在的目录（也就是错误提示中的"xxx/xxx"目录"），然后执行“svn upgrade”。看到执行结果输出Upgraded ‘.’就行了。
Upgraded ‘.’
