llvm dev - Jul 2018 - clang-format as an Arcanist linter; need reviewers

Siddhartha Bagaria has posted https://reviews.llvm.org/D49116
to implement this, with my encouragement. However, I don't know 
anything about arcanist (and not much about clang-format!) 
Can somebody please look at this patch?
Thanks!
--paulr