silverstripe/sapphire — comment on commit 8fa266462f2ef3aac5065045649f75f776498728
File: forms/CheckboxSetField.php line 190
By chillu:

The dev cycle was "Copy code to ListboxField to make it work properly with relations, find out its a pain in the ass, try to cram it into CheckboxSetField" ;)
I figured it was too much of a distraction to fix up ListboxField for the goal at hand, but done that now in 6e3ceefbb86b048bb9b12b414103fa578a8f2504, and reverted this commit. Also, I assume your envisioned MultiItemSelectField matches the existing ListboxField?