Have undo switch files so you can undo changes made to multiple files in the order they were made.

Web development encourages file modularization, which results in many files each holding small amounts of code. This means you end up making a sequence of changes to multiple javascript, css, html (etc) files to implement a single change. If you do this and the changes together break your project you suddenly need to remember which files you changed and in which order.

It would be great to have an undo command that remembered changes in a time series that included the sequence of files that were changed. Thus each time you issued the undo command the previous file changed would open (if it's not already open) and the undo would occur.