Merge branch 'cc/bisect' (early part)

Merge branch 'cc/bisect' (early part)

* 'cc/bisect' (early part):
  bisect: make "git bisect" use new "--next-all" bisect-helper function
  bisect: add "check_good_are_ancestors_of_bad" function
  bisect: implement the "check_merge_bases" function
  bisect: automatically sort sha1_array if needed when looking it up
  bisect: make skipped array functions more generic
  bisect: remove too much function nesting
  bisect: use new "struct argv_array" to prepare argv for "setup_revisions"
  bisect: store good revisions in a "sha1_array"
  bisect: implement "rev_argv_push" to fill an argv with revs
  bisect: use "sha1_array" to store skipped revisions
  am: simplify "sq" function by using "git rev-parse --sq-quote"
  bisect: use "git rev-parse --sq-quote" instead of a custom "sq" function
  rev-parse: add --sq-quote to shell quote arguments
  rev-list: remove stringed output flag from "show_bisect_vars"
  bisect--helper: remove "--next-vars" option as it is now useless
  bisect: use "git bisect--helper --next-exit" in "git-bisect.sh"
  bisect--helper: add "--next-exit" to output bisect results
  bisect: move common bisect functionality to "bisect_common"
  rev-list: refactor printing bisect vars
  rev-list: make "estimate_bisect_steps" non static