Google may be assembling a supergroup of big retail brands to go to war with Amazon over the future of online shopping. Reuters is reporting that the search engine is teaming up with Target, Walmart, Home Depot, Costco and Ulta for the new project. These companies, and any other willing participants, can index their catalogs on Google, which will show up when someone starts searching for stuff to buy. Naturally, rather than receiving an ad fee, Google simply gets a cut of the sales that are subsequently generated. This program is an extension of the existing Google Shopping ads that show up when you search for a product — they’re separate from the organic search listings, instead showing up in a dedicated shopping sidebar.