Put a wall on a new axis, retaining cuts only at unchanged ends with the
same direction. Cuts are distances from their OWN end, so extending Start
does not rebase EndCut. Changed ends start square before a join recuts them.
Shared by the canonical editor and its preview (#6232/#6535).
Put a wall on a new axis, retaining cuts only at unchanged ends with the same direction. Cuts are distances from their OWN end, so extending Start does not rebase EndCut. Changed ends start square before a join recuts them. Shared by the canonical editor and its preview (#6232/#6535).