Black and white flag at Tour de France

I’ve done some searching for this and can’t find anything. At the Tour de France, which I watch every afternoon in July, I see fans waving flags in the pattern of the American flag, but with black and white stripes and what appear to be about twelve small pine trees on a white field. I’ve been seeing this for the past several years. As far as I know it’s not a Basque or Catalan separatist flag, and as far as I know it doesn’t represent any of the teams. I can’t figure out what it means, and I see it several times every day. This is starting to get on my nerves. Please help.

You’re likely seeing the Breton flag .