Kayia (kayia.org) is a spreadsheet/reactive programming environment but where the code can be 'diff'ed. All values in the spreadsheet are versioned, so you can

Kayia (kayia.org) is a spreadsheet/reactive programming environment but where the code can be 'diff'ed. All values in the spreadsheet are versioned, so you can either look at the current value of, say, Cell B2 or its immutable value at a specific point in time, or see how its value has changed over time. And since the code is stored in the same way as the data, version control of the source is a first-class part of the language.