commits="updated from $(git describe --always "$old") -> $(git describe --always "$new")"
elif [ "$new" = "$(git merge-base "$old" "$new")" ]; then # rollback
commits="!! rolled back to $(git describe --always "$new") erasing history through $(git describe --always "$old")"
commits="updated from $(git describe --always "$old") -> $(git describe --always "$new")"
elif [ "$new" = "$(git merge-base "$old" "$new")" ]; then # rollback
commits="!! rolled back to $(git describe --always "$new") erasing history through $(git describe --always "$old")"