It is hard to manipulate pairs of files without special container. For example, you want to attach chages to e-mail, changes cover 10 files + 1 removed file + 2 added files. Will you pack it to tar/zip with two folders `old` and `new` inside or what? Looks like pre-VCS era solution, when we did manaul "version control" by copying `project` to `project-19950112-final-for-sure` :)