Merge branch 'cc/bisect'

Merge branch 'cc/bisect'

* cc/bisect:
  Bisect reset: do nothing when not bisecting.
  Bisect: use "$GIT_DIR/BISECT_NAMES" to check if we are bisecting.
  Bisect visualize: use "for-each-ref" to list all good refs.
  git-bisect: modernize branch shuffling hack
  git-bisect: use update-ref to mark good/bad commits
  git-bisect: war on "sed"
  Bisect reset: remove bisect refs that may have been packed.