Version Control with Git

Precedents

The complete history of version control systems is beyond the scope of this book. However, there are several landmark, innovative systems that set the stage for or directly led to the development of Git. (This section is selective, hoping to record when new features were introduced or became popular within the free software community.)

The Source Code Control System (SCCS) was one of the original systems on Unix and was developed by M. J. Rochkind in the very early 1970s.^[1] This is arguably the first VCS available on any Unix system.

The central store that SCCS provided was called a repository, and that fundamental concept remains pertinent to this day. SCCS also provided a simple locking model to serialize development. If a developer needed files to run and test a program, she would check them out unlocked. However, in order to edit a file, she had to check it out with a lock (a convention enforced through the Unix filesystem). When finished, she would check the file back into the repository and unlock it.

In the early 1980s, Walter Tichy introduced the Revision Control System (RCS)^[2] RCS introduced both forward and reverse delta concepts for efficient storage of different file revisions.

The Concurrent Version System (CVS), designed and originally implemented by Dick Grune in 1986 and then crafted anew some four years later by Berliner et al., extended and modified the RCS model with great success. CVS became very popular and was the de facto standard within the open ...