Don’t ask punk-turned-folky-blues-troubadour Saint Andrew how he wound up on a bill full of rappers. But here he is. You may recognize him from his days with Knifedance and Stepsister, or more recently from the corner of St. Clair and West Sixth streets, where he busks every Friday and Saturday night, playing guitar and harmonica, and tussling with belligerent panhandlers. Yeah, he’s that guy.