Array moves can sometimes be hard to understand

[thorning]

The longest common sequence used in array moves makes some deltas quite confusing to understand.

Take for example a change from [1,2,3] => [3,2,1], which result in the following delta: { _t: 'a', _1: [ '', 1, 3 ], _2: [ '', 0, 3 ] }

Here the 1 is not "moved" and the 2 and 3 is "moved" in front of it. This is right, but hard to wrap your head around at first sight.

I made a pullrequst, #145 , that accepts an option to explicitly state all differences between arrays. The above delta will then become { _t: 'a', _0: [ '', 2, 3 ], _2: [ '', 0, 3 ] }

The disadvantage is obviously that an insert at the start of the array causes every other element to shift, and results in some rather large deltas.

It might be possible fo add a new delta types for arrays, group-moves, which specifies groups that are moved together. This would mean an insert at the start of an array would have a delta of one insert and one group move.

I have not looked enough through the code to know how much impact this would have on I.e. formaters.