shape-doctor.py: a root whose index holds an unmerged path gets a merge FINDING naming the paths, with git -C <root> status as its NEXT, and the verdict INVALID (merge), exit 1, on a rung above every other but CANNOT ANSWER, so a merge git commit refuses no longer reads COMPLIANT, exit 0, once checkout --ours takes the markers out, or DRIFTED about a leg that never moved (#424) - #468