Revision Control System

Last updated
Revision Control System
Original author(s) Walter F. Tichy
Developer(s) GNU Project
The OpenBSD project (OpenRCS)
Initial release1982;42 years ago (1982)
Stable release
5.10.1 [1] / 2 February 2022;2 years ago (2 February 2022)
Repository
Written in C
Operating system Unix-like, V [2]
Type Version control
License GPL-3.0-or-later [lower-alpha 1] [3]
2-clause BSD license (OpenRCS)
Website www.gnu.org/software/rcs/

Revision Control System (RCS) is an early implementation of a version control system (VCS). It is a set of UNIX commands that allow multiple users to develop and maintain program code or documents. With RCS, users can make their own revisions of a document, commit changes, and merge them. RCS was originally developed for programs but is also useful for text documents or configuration files that are frequently revised. [4]

Contents

History

Development

RCS was first released in 1982 [4] by Walter F. Tichy at Purdue University. It was an alternative tool to the then-popular Source Code Control System (SCCS) which was nearly the first version control software tool (developed in 1972 by early Unix developers). [5] RCS is currently maintained by the GNU Project. [6]

An innovation in RCS is the adoption of reverse deltas. Instead of storing every revision in a file like SCCS does with interleaved deltas, RCS stores a set of edit instructions to go back to an earlier version of the file. Tichy claims that it is faster for most cases because the recent revisions are used more often. [4]

Initially (through version 3, which was distributed in 4.3BSD), its license prohibited redistribution without written permission from Walter Tichy: [7]

Copyright (C) 1982 by Walter F. Tichy [...] All rights reserved. No part of this software may be sold or distributed in any form or by any means without the prior written permission of the author.

A READ_ME file accompanied some versions of RCS which further restricted distribution, e.g., in 4.3BSD-Reno. [8]

Ca. 1989, the RCS license was altered to something similar to the contemporary BSD licenses, as seen by comments in the source code. [9]

Redistribution and use in source and binary forms are permitted provided that the above copyright notice and this paragraph are duplicated in all such forms and that any documentation, advertising materials, and other materials related to such distribution and use acknowledge that the software was developed by Walter Tichy.

RCS 4.3, released 26 July 1990, was distributed "under license by the Free Software Foundation", under the terms of the GPL. [10] [ full citation needed ]

OpenBSD provides a different implementation called OpenRCS, which is BSD-licensed. [11]

Behavior

Mode of operation

RCS operates only on single files. It has no way of working with an entire project, so it does not support atomic commits affecting multiple files. Although it provides branching for individual files, the version syntax is cumbersome. Instead of using branches, many teams just use the built-in locking mechanism and work on a single head branch. [4]

Usage

RCS revolves around the usage of "revision groups" or sets of files that have been checked-in via the co (checkout) and ci (check-in) commands. By default, a checked-in file is removed and replaced with a ",v" file (so foo.rb when checked in becomes foo.rb,v) which can then be checked out by anyone with access to the revision group. RCS files (again, files with the extension ",v") reflect the main file with additional metadata on its first lines. Once checked in, RCS stores revisions in a tree structure that can be followed so that a user can revert a file to a previous form if necessary. [4]

Advantages

Disadvantages

Notes

  1. ↑ GPL-3.0-or-later since 2010-06-24.

See also

Related Research Articles

Concurrent Versions System is a version control system originally developed by Dick Grune in July 1986.

Version control is the software engineering practice of controlling, organizing, and tracking different versions in history of computer files; primarily source code text files, but generally any type of file.

<span class="mw-page-title-main">Apache Subversion</span> Free and open-source software versioning and revision control system

Apache Subversion is a version control system distributed as open source under the Apache License. Software developers use Subversion to maintain current and historical versions of files such as source code, web pages, and documentation. Its goal is to be a mostly compatible successor to the widely used Concurrent Versions System (CVS).

<span class="mw-page-title-main">History of software configuration management</span>

The history of software configuration management (SCM) can be traced back as early as the 1950s, when CM, originally for hardware development and production control, was being applied to software development. Early software had a physical footprint, such as cards, tapes, and other media. The first software configuration management was a manual operation. With the advances in language and complexity, software engineering, involving configuration management and other methods, became a major concern due to issues like schedule, budget, and quality. Practical lessons, over the years, had led to the definition, and establishment, of procedures and tools. Eventually, the tools became systems to manage software changes. Industry-wide practices were offered as solutions, either in an open or proprietary manner. With the growing use of computers, systems emerged that handled a broader scope, including requirements management, design alternatives, quality control, and more; later tools followed the guidelines of organizations, such as the Capability Maturity Model of the Software Engineering Institute.

patch (Unix) Unix utility to apply changes to text files

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Source Code Control System (SCCS) is a version control system designed to track changes in source code and other text files during the development of a piece of software. This allows the user to retrieve any of the previous versions of the original source code and the changes which are stored. It was originally developed at Bell Labs beginning in late 1972 by Marc Rochkind for an IBM System/370 computer running OS/360.

GNU Readline is a software library that provides in-line editing and history capabilities for interactive programs with a command-line interface, such as Bash. It is currently maintained by Chet Ramey as part of the GNU Project.

CVSNT is a version control system compatible with and originally based on Concurrent Versions System (CVS), but whereas that was popular in the open-source world, CVSNT included features designed for developers working on commercial software including support for Windows, Active Directory authentication, reserved branches/locking, per-file access control lists and Unicode filenames. Also included in CVSNT were various RCS tools updated to work with more recent compilers and compatible with CVSNT.

The Distributed Concurrent Versions System (DCVS) was a distributed revision control system that enables software developers working on locally distributed sites to efficiently collaborate on a software project. DCVS was based on the well known version control system Concurrent Versions System. The code was freely distributable under the GNU and BSD style licenses. The project was terminated sometime before late 2023.

The following tables describe attributes of notable version control and software configuration management (SCM) software systems that can be used to compare and contrast the various systems.

<span class="mw-page-title-main">Free-software license</span> License allowing software modification and redistribution

A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and redistribute that software. These actions are usually prohibited by copyright law, but the rights-holder of a piece of software can remove these restrictions by accompanying the software with a software license which grants the recipient these rights. Software using such a license is free software as conferred by the copyright holder. Free-software licenses are applied to software in source code and also binary object-code form, as the copyright law recognizes both forms.

<span class="mw-page-title-main">Berkeley Software Distribution</span> Unix operating system

The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley. Since the original has become obsolete, the term "BSD" is commonly used for its open-source descendants, including FreeBSD, OpenBSD, NetBSD, and DragonFly BSD.

BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD license was used for its namesake, the Berkeley Software Distribution (BSD), a Unix-like operating system. The original version has since been revised, and its descendants are referred to as modified BSD licenses.

<span class="mw-page-title-main">GNU General Public License</span> Series of free software licenses

The GNU General Public Licenses are a series of widely used free software licenses, or copyleft licenses, that guarantee end users the freedoms to run, study, share, and modify the software. The license was the first copyleft for general use and was originally written by Richard Stallman, the founder of the Free Software Foundation (FSF), for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition. The licenses in the GPL series are all copyleft licenses, which means that any derivative work must be distributed under the same or equivalent license terms. It is more restrictive than the Lesser General Public License and even further distinct from the more widely-used permissive software licenses such as BSD, MIT, and Apache.

<span class="mw-page-title-main">Unix filesystem</span> Directory structure used by a Unix-like operating system

In Unix and operating systems inspired by it, the file system is considered a central component of the operating system. It was also one of the first parts of the system to be designed and implemented by Ken Thompson in the first experimental version of Unix, dated 1969.

<span class="mw-page-title-main">NetBSD</span> Free and open-source Unix-like operating system

NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems.

<span class="mw-page-title-main">Meld (software)</span>

Meld is a visual diff and merge tool, targeted at developers. It allows users to compare two or three files or directories visually, color-coding the different lines.

Software relicensing is applied in open-source software development when software licenses of software modules are incompatible and are required to be compatible for a greater combined work. Licenses applied to software as copyrightable works, in source code as binary form, can contain contradictory clauses. These requirements can make it impossible to combine source code or content of several software works to create a new combined one.

The history of the Berkeley Software Distribution begins in the 1970s.

References

  1. ↑ Thien-Thi Nguyen (2 February 2022). "GNU RCS 5.10.1 available" . Retrieved 3 February 2022.
  2. ↑ V-System 6.0 Reference Manual
  3. ↑ "Update license to GPLv3+". 24 June 2010.
  4. 1 2 3 4 5 Tichy, Walter (1982). "Design, implementation, and evaluation of a Revision Control System". ICSE '82 Proceedings of the 6th International Conference on Software Engineering: 58–67. Retrieved 12 June 2012.
  5. ↑ Raymond, Eric. "Understanding Version-Control Systems (DRAFT)". www.catb.org. Retrieved 13 February 2017.
  6. ↑ "RCS". GNU Project. Free Software Foundation. 22 January 2015. Retrieved 27 June 2015.
  7. ↑ "4.3BSD - /usr/src/new/rcs/src/rcsdiff.c". Walter's Retro Computing Corner Documentation. 19 May 1986. Retrieved 15 November 2014.
  8. ↑ "CSRG/cd2/4.3reno/usr/src/contrib/rcs/src/READ_ME". 27 February 1989.
  9. ↑ "CSRG/cd2/4.3reno/usr/src/contrib/rcs/src/rcs.c". 15 August 1989.
  10. ↑ RCS 4.3 README file.
  11. ↑ "rcs(1) - OpenBSD manual pages". man.openbsd.org. Retrieved 5 September 2024.
  12. 1 2 3 "Revision control concepts – Revision Control System (RCS), Concurrent Versions System (CVS) and Subversion". IT PASSION - "IT professional Blog". 10 December 2008. Retrieved 20 February 2017.
  13. ↑ Steinberg, Frank. "Revision Control Systems (RCS, CVS, Subversion, Git)". Technical University of Braunschweig . Retrieved 20 February 2017.

Notes

Further reading

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