Learning GNU Emacs, 3rd Edition

Chapter 12. Version Control

The Uses of Version Control

If you write either large programs or long documents, you have probably been caught at least once in a situation where you've made changes that turned out to be a bad thing, only to be confused and stymied because you weren't sure exactly how to reverse them and get back to a known good state. Or, perhaps you've released a program or document to someone else, then gotten a bug fix or a comment that you couldn't integrate properly because you couldn't recover the old version that person was working with. Perhaps you're a member of a development or documentation team and have felt the need for some way to keep change histories, indicating who was responsible for each change.

These common kinds of problems can be addressed with a version control system. A version control system gives you automated help at keeping a change history for a file or group of files. It allows you to recover any stage in that history, and it makes getting reports on the differences between versions easy.

Today a variety of version control systems are widely available on machines that run Emacs. Some are commercial, but there are a wealth of free, open, and powerful choices, and it seems appropriate for our discussion to focus on these. Historically, Emacs evolved largely in a Unix environment alongside the SCCS and RCS systems, and its built-in support for version control reflects their approach and terminology. Today the most popular by far is CVS (which ...