What does the autotest autoupdate module do?

https://github.com/seattlerb/zentest/blob/master/lib/autotest/autoupdate.rb

It's not documented and I开发者_StackOverflow中文版 can't find any discussion about it on the web.

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It runs the @@update_cmd (by default: svn up) every @@sleep_time seconds (by default: 60).