Who is Joshua Deets from Lonesome Dove and what is their importance?

Deets is a large black man with very white teeth. He wears pants made from old quilts that have cotton ticking that sticks out all over the place, and an old cavalry cap that he had found somewhere back in the fifties as close as anyone could remember. Deets wasn't the type to give up on a garment just because it had a little age.