best way for you is to grab a Notepad papers what ever you can get ur ink on and Try to write down your events So that you can See where you changes things and or a power outage Causing to lose data or computer crash etc or a cat ate your computer.
I prefer writing my events down and or sometimes if i like the set of events to make something happen ill record it for future uses with a good comment on what it can be used for.
Think of it like old school back up copy
I was not referring to a history of changes. Perhaps I have not expressed very well.
Only say that the focus is where the action is in the code. In this case the Undo or redo it.
Another issue I see very necessary when working on a project several people, is able to compare projects, for example through xml files. Meld or WinMerge and similar programs often give bad results and wastes time.
But this is changing the subject and almost go offtopic, sorry.