Merge branch 'cc/bisect-filter' (early part) into next

Merge branch 'cc/bisect-filter' (early part) into next

* 'cc/bisect-filter' (early part):
  rev-list: pass "revs" to "show_bisect_vars"
  rev-list: make "show_bisect_vars" non static
  rev-list: move code to show bisect vars into its own function
  rev-list: move bisect related code into its own file
  rev-list: make "bisect_list" variable local to "cmd_rev_list"
  refs: add "for_each_ref_in" function to refactor "for_each_*_ref" functions
  quote: add "sq_dequote_to_argv" to put unwrapped args in an argv array
  quote: implement "sq_dequote_many" to unwrap many args in one string