woothemes/woocommerce — pull request #703 by pixeltrix (2012-02-25 08:12:53+00:00)
Title: Add previous price to on-sale variable product

As discussed in #647.

One thing I haven't addressed is whether you want to add an upgrade hook to add the new meta data to existing products - is that something you'd want? Also the previous variable price filter only gets called for prices that match the old format - do you want it called for all variable prices? There's an argument either way for backwards compatibility - existing sites may be expecting it to be a certain format or to be called for all variable prices (or both!).