Merge branch 'rs/pickaxe'

* rs/pickaxe:
  pickaxe: factor out pickaxe
  pickaxe: give diff_grep the same signature as has_changes
  pickaxe: pass diff_options to contains and has_changes
  pickaxe: factor out has_changes
  pickaxe: plug regex/kws leak
  pickaxe: plug regex leak
  pickaxe: plug diff filespec leak with empty needle