Merge branch 'ab/bisect-cleanup'

Code clean-up. * ab/bisect-cleanup: bisect: no longer try to clean up left-over `.git/head-name` files bisect: remove Cogito-related code bisect run: fix the error message bisect: verify that a bogus option won't try to start a bisection bisect--helper: make the order consistently `argc, argv` bisect--helper: simplify exit code computation