I use a text editor for my long to do list, and wish to keep record of what items get removed off it. However, don't want to have multiple copies of the 1/4Mb file existing on storage media. Is there any text editor that will only save the changes since a base copy (I would keep this editor up 24/7, if that helps the "Which file would it use for a base copy?" question)
Would also be nice if this program was capable of facilitating a large undo/redo history.
Does a open source and/or freeware option exist?