Table of Contents
“It is important not to let the perfect become the enemy of the good, even when you can agree on what perfect is. Doubly so when you can't. As unpleasant as it is to be trapped by past mistakes, you can't make any progress by being afraid of your own shadow during design.” | ||
| --Greg Hudson | ||
In the world of open-source software, the Concurrent Versions System (CVS) was the tool of choice for version control for many years. And rightly so. CVS was open-source software itself, and its non-restrictive modus operandi and support for networked operation allowed dozens of geographically dispersed programmers to share their work. It fit the collaborative nature of the open-source world very well. CVS and its semi-chaotic development model have since become cornerstones of open-source culture.
But CVS was not without its flaws, and simply fixing those flaws promised to be an enormous effort. Enter Subversion. Designed to be a successor to CVS, Subversion's originators set out to win the hearts of CVS users in two ways—by creating an open-source system with a design (and “look and feel”) similar to CVS, and by attempting to avoid most of CVS's noticeable flaws. While the result isn't necessarily the next great evolution in version control design, Subversion is very powerful, very usable, and very flexible. And for the most part, almost all newly-started open-source projects now choose Subversion instead of CVS.
This book is written to document the 1.4 series of the Subversion version control system. We have made every attempt to be thorough in our coverage. However, Subversion has a thriving and energetic development community, so there are already a number of features and improvements planned for future versions of Subversion that may change some of the commands and specific notes in this book.
This book is written for computer-literate folk who want to use Subversion to manage their data. While Subversion runs on a number of different operating systems, its primary user interface is command-line based. That command-line tool (svn) and auxiliary program are the focus of this book.
For consistency, the examples in this book assume the reader
is using a Unix-like operating system and relatively comfortable
with Unix and command-line interfaces. That said, the
svn program also runs on non-Unix platforms
like Microsoft Windows. With a few minor exceptions, such as
the use of backward slashes (\) instead of
forward slashes (/) for path separators, the
input to and output from this tool when run on Windows are
identical to its Unix counterpart.
Most readers are probably programmers or system administrators who need to track changes to source code. This is the most common use for Subversion, and therefore it is the scenario underlying all of the book's examples. But Subversion can be used to manage changes to any sort of information—images, music, databases, documentation, and so on. To Subversion, all data is just data.
While this book is written with the assumption that the reader has never used a version control system, we've also tried to make it easy for users of CVS (and other systems) to make a painless leap into Subversion. Special sidebars may mention other version control systems from time to time, and a special appendix summarizes many of the differences between CVS and Subversion.
Note also that the source code examples used throughout the book are only examples. While they will compile with the proper compiler incantations, they are intended to illustrate a particular scenario, not necessarily serve as examples of good programming style or practices.