Re: undo an undo

[Stefan Monnier]

> It might be better to point out that the undo history is not a stack;

Indeed, it's more like a tree, in the sense that when you undo something you
go back towards the root and future changes will be recorded as a new
branch.  But since the undo itself is a change, it is also recorded in the
tree at the tip of the current branch.  So you really get a big ugly
directed acyclic graph.


        Stefan