Since Subversion caches auth credentials by default (both username and password), it conveniently remembers who you were acting as the last time you modified your working copy. But sometimes that’s not helpful—particularly if you’re working in a shared working copy such as a system configuration directory or a web server document root. In this case, just pass the --username option on the command line, and Subversion will attempt to authenticate as that user, prompting you for a password if necessary.