this boils down to the two alternatives
- manipulate the target data structure
- build an altered copy
since our goal is to handle large tree structures efficiently,
the decision was cast in favour of data manipulation
As decided in beb57cde
this changeset switches our basic list diff language to work
in the style of an insertion sort. Rather than 'pushing back'
out-of-order elements, we scan and bring forward missing elements.
Later, when passing the original location of the elements
fetched this way, a 'skip' verb will help to clean up
possible leftowers, so implementation is possible
(and indeed acomplished) without shifting any other elements.
