Merge branch 'jc/bisect'

Merge branch 'jc/bisect'

* jc/bisect:
  make the previous optimization work also on path-limited rev-list --bisect
  rev-list --bisect: Fix "halfway" optimization.
  t6004: add a bit more path optimization test.
  git-rev-list --bisect: optimization
  git-rev-list: add --bisect-vars option.
  t6002: minor spelling fix.