There is no writing credit for “Sportin’ Life,” which feels like an omission, but an apt one. On the one hand, this documentary self-portrait by rogue auteur Abel Ferrara feels wholly the product of his eccentric imagination, colored by his voice from beginning to hasty end. On the other, it’s impossible to imagine such a chaotic, clashing assemblage of half-thoughts and impulses being “written” per se: A video diary of the filmmaker’s travels and stasis from February to August of this year, edited with nary a moment to reflect ahead of its premiere at the Venice Film Festival this month, it gives every appearance of having been downloaded directly from his brain in its full antic, distracted form. Whose 2020 has been a year of tidy ideas, after all?