metabrainz/CAA-indexer — pull request #10 by ianmcorvidae (2014-02-24 23:14:04+00:00)
Title: Use the x-archive-keep-old-version header when making requests to the IA; this preserves the files in a special history folder.

This is documented on http://archive.org/help/abouts3.txt and we were talking about it probably being a good idea the other day.