PRCS(1)

NAME
prcs - Invoke the Project Revision Control System

SYNOPSIS
prcs subcommand [ option... ] [ operand... ]

DESCRIPTION
The Project Revision Control System, PRCS, is the front end to a set of tools that (like CVS) provide a way to deal with sets of files and directories as an entity, preserving coherent versions of the entire set. The command prcs executes the various functions (subcommands) of the the system.

Abstractly, PRCS presents you ("the user") with the abstraction of named projects that have multiple (project) versions, each of which is a set of files, arranged into a directory subtree. A project is the collection of all project versions of that project. Each project version contains one distinguished file, called the (project) version descriptor, in the top directory of the subtree, which contains a description of the files included in that particular version. For a project named P, this file has the name P.prj (and so is also called a ".prj file").

  Functions Provided
The subcommands provided allow you to perform the following actions:

•   Create a copy of the directory tree (or a part of it) for a given project version. The files in such a copy are called working files and the root directory for these working files is called a working directory. This process is called checking-out the version (or the working files). You may select a project version to check out by its version number. Modifying the working files has no effect on the project version they came from.

•   Create a new project version (and a new project, for the first version) from working files, or from some mix of working files and the files in a another project version. This is called checking-in the version (or the working files). Before any check-in, PRCS checks to see if there have been other modifications to files in this project and warns you of conflicts and discrepancies.

•   Search for differences between a project version and working files or between the files in two versions of a project.

•   Insert changes that occurred between two project versions into working files. This process is called merging because its purpose is to combine changes you have made to a set of working files with changes that others have made in the meantime. It changes only the working files, because in general they will need editting to reconcile places where the two sets of changes conflict. The resulting merged files are marked with distinctive lines indicating places where the two sets of changes that are being combined differ from each other. One typically edits the merged files to reconcile the differences, and then checks in a new version.

•   Print out information about the versions of a project contained in the repository.

In addition, you may add and subtract the files contained in a new project version, or move files from one subdirectory to another by editing the working copy of the .prj file before checking in the new version.

PRCS keeps all checked-in project versions in a projects repository. At any given time, you fix a prevailing repository by setting the environment variable PRCS_REPOSITORY (which defaults to $HOME/PRCS), and do not explicitly mention it in any commands.

Each checked-in version has a version name of the form M.N. Here, M, the major version name, is an alphanumeric label--either a numeral or a label beginning with a letter and consisting of letters, digits, and the characters
    # % ^ - _ + = : , . --and N, the minor version name, is a non-negative numeral. PRCS assigns minor version names automatically in sequence. Major version names are up to the user; by default, they also are numerals.

PRCS uses the approach found in CVS (Concurrent Version System): unlike version control systems such as RCS and SCCS, PRCS locks projects in the repository only while it is actually running (in order to make operations on projects atomic). One simply checks in new versions as desired; the system will warn you if others have made parallel changes to the major version of the project you are working on that may have to be merged with changes you have made.

Where PRCS differs from CVS (and, indeed, other source-code control systems of the author's acquaintance) is in its attempt to provide a particularly simple model to the user. A project is a collection of files, period. Although the current implementation of PRCS actually uses RCS in its implementations, none of the details of RCS are of any consequence to the user.

  Basic Use
For a complete description of the subcommands, options, files, and environment variables of PRCS, see the TexInfo pages provided with the release. Here is a brief overview of typical, simple use of the system, which may suffice for many users.

The simplest possible use of prcs is just to use it to keep a single thread of project versions, thus allowing you to ``roll back'' at any time, and allowing multiple people to do maintenance on a single system simultaneously.

To start things off with a new project, P1, type % prcs checkout P1 in the working directory where you are developing your project. (If you haven't yet established a repository, PRCS will create one.) The effect of this command is to create a working version descriptor file by the name P1.prj with an empty list of files. The version descriptor contains, among other things, a list of the names of all files in a particular version of the project (called the Files list).

If the project was already underway before you created a PRCS project for it, you will probably want to start off by adding the names of your existing files to this list to bring them under version control. To do so, type % prcs populate P1 or, if there is only one .prj file, simply % prcs populate Edit the file P1.prj (with your favorite text editor) as needed to remove any files you don't want to control (like .o files, back-up files, and executables). You can also specify the list of files in the population on the command line. The files in any directories in this list will be included recursively: % prcs populate P1 file1 file2 Whenever you want to checkpoint your project, type % prcs checkin P1 # or just prcs checkin from the root working directory (the one with P1.prj in it). This creates (in effect) a new version in the repository containing copies of the files listed in P1.prj, and updates P1.prj to reflect the new version's name. You may specify a new major version name at checkin time with the -r option: % prcs checkin -rMyVersion P1 If someone else has checked in files in the meantime, you will be notified of discrepancies, which you can handle by typing % prcs merge from the root working directory and (after it's done), editing the files.

Whenever it comes time to begin working on a deposited version of the project, you can go to a clean directory and check out the latest version with % prcs checkout P1 or, if you want a major version other than the (numeric) default, % prcs checkout -rMyVersion P1 Now you can make any desired modifications and check in as before.

ENVIRONMENT

PRCS_REPOSITORY
    Path to the repository. Defaults to $HOME/PRCS.

IDENTIFICATION
Author: Paul N. Hilfinger and Josh MacDonald
Manual Page Revision: 1.5; Release Date: Sun, 09 May 2004 18:34:01 -0700.
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