Content from The College

Version Control

• about 2/3 of the cost of a software product is spent on maintenance

• maintenance involves revising source code and generating new
executables
• sometimes changes need to be undone and an earlier version recalled
• there may be several versions of softare in production while new ones
are being developed
• such complex systems need version control to help avoid problems

cvs (Concurrent Versions System)

• cvs controls who is allowed to update files

• for each update, the programmer and reason for change are recorded
• the most recent version of each file is stored with sufficient information
to recreate all previous versions
• versions of several files may be grouped together into releases
• storing changes to files saves considerable disk space over saving
complete versions of files
• purpose of each cvs command can be displayed using cvs * -H
• to get help on an individual command, use cvs -H command
• the examples use the same sample programs as used in the creation of
libraries: prog2.h f1.c f2.c prog2.c
• cvs commands:
o init - create a source repository, for example:

cvs -d ~/cvsroot init

▪ instead of using "-d" option, could set environment
variable: export CVSROOT=~/cvsroot
▪ remaining commands assume that "CVSROOT" has been
set and exported
▪ "cvsroot" is often used but can be anything; it would not
normally be in a user's home directory in a multi-
programmer project
▪ specified directory must be an absolute path name
o import - import source files into repository, for example:
 cvs import -m "Import source files"
prog2dir vendor-tag start
▪"-m" option specifies message to write to history files
▪ "prog2dir" is the directory within the repository to place the
source files, also called a "module"
▪ "vendor-tage" is a vendor tag, useful when working with
software developed elsewhere
▪ "start" must be specified
▪ all the files in the current directory will be copied
appropriately, then the original source files should be
deleted to avoid confusion
o example of creating a repository and importing source files:
o ==> ls
o f1.c f2.c prog2.c prog2.h
o ==> export CVSROOT=~/cvsroot
o ==> cvs init
o ==> cvs import -m "Import source
files" prog2dir vendor-tag start
o N prog2dir/prog2.c
o N prog2dir/prog2.h
o N prog2dir/f1.c
o N prog2dir/f2.c
o

o No conflicts created by this import

o

o ==> rm *
o ==> ls
o ==> _

o checkout - checkout source files into our "sandbox", for example:

cvs checkout prog2dir

 ▪ all the files in the module "prog2dir" will be checked out, into
a subdirectory called "prog2dir"
▪ can checkout individual files, for example: cvs
checkout prog2dir/prog2.c
o example of checking out a module:
o ==> mkdir ~/sandbox
o ==> cd ~/sandbox
o ==> cvs checkout prog2dir
o cvs checkout: Updating prog2dir
o U prog2dir/f1.c
o U prog2dir/f2.c
o U prog2dir/prog2.c
o U prog2dir/prog2.h
o ==> ls
o prog2dir
o ==> cd prog2dir
o ==> ls
o CVS f1.c f2.c prog2.c prog2.h
o ==> _

o commit - commit changes made to source files in sandbox, for

example:

cvs commit -m "Added a comment"

prog2.c
▪"-m" option specifies message to write to history files
▪ if not in "prog2dir" directory, path to "prog2.c" must be
included
▪ this will fail if "prog2.c" has been changed by another user
since it was checked out
o example of changing a file (added a comment to "prog2.c") and
committing:
o ==> cvs commit -m "Added a comment"
prog2.c
o

/home/lczegel/cvsroot/prog2dir/prog2
.c,v <-- prog2.c
o new revision: 1.2; previous
revision: 1.1
o ==> _

o update - merge changes with source that was changed since it

was checked out, for example:

cvs update prog2.c

▪ this will create a new file with both sets of changes, you
must decide how to merge them, then commit
o add - add new files to repository, for example:

cvs add makefile makefile2

▪this will mark "makefile" and "makefile2" for inclusion in
repository, then they must be commited
▪ if an entire directory is added, it doesn not need to be
committed
o example of adding new files and committing:
o ==> cp ~lczegel/UNIX/makefile
~lczegel/UNIX/makefile2 .
o ==> cvs add makefile makefile2
o cvs add: scheduling file `makefile'
for addition
o cvs add: scheduling file
`makefile2' for addition
o cvs add: use `cvs commit' to add
these files permanently
o ==> cvs commit -m "Added makefiles"
makefile makefile2
o

/home/lczegel/cvsroot/prog2dir/makef
ile,v <-- makefile
o initial revision: 1.1
o

/home/lczegel/cvsroot/prog2dir/makef
ile2,v <-- makefile2
o initial revision: 1.1
o ==> _

o rtag - freeze a release, for example:

cvs rtag Release_1 prog2dir

▪this will allow extracting the current source files, regardless
of any additional development
▪ "-F" option will move tag if it already exists
▪ "-d" option will delete the tag
o example of freezing a release:
o ==> cvs rtag Release_1 prog2dir
o cvs rtag: Tagging prog2dir
o ==> _

o remove - remove files from repository, for example:

cvs remove makefile

 ▪this will mark "makefile" for removal from repository, then it
must be commited
▪ the files must be removed from the sandbox before they can
be removed from the repository
o example of removing a file from the repository:
o ==> rm makefile
o ==> cvs remove makefile
o cvs remove: scheduling `makefile'
for removal
o cvs remove: use `cvs commit' to
remove this file permanently
o ==> cvs commit -m "Removing
makefile" makefile
o

/home/lczegel/cvsroot/prog2dir/makef
ile,v <-- makefile
o new revision: delete; previous
revision: 1.1
o ==> _

o diff - display differences, for example:

cvs diff -c prog2.c

▪ this will display differences between source file in sandbox
and in repository
o example of changing a file (added another comment to "prog2.c")
then displaying the differences::
o ==> cvs diff -c prog2.c
o Index: prog2.c
o

====================================
===============================
o RCS file:
/home/lczegel/cvsroot/prog2dir/prog2
.c,v
o retrieving revision 1.2
o diff -c -r1.2 prog2.c
o *** prog2.c 9 Mar 2007 23:59:12
-0000 1.2
o --- prog2.c 10 Mar 2007
00:14:45 -0000
o ***************
o *** 1,6 ****
o --- 1,7 ----
o #include <stdlib.h>
o #include "prog2.h"
o /* this is the first comment
added */
o + /* this is another comment to
display differences */
o int main(void) {
o int num2;
o num2 = f1();
o ==> _

o export - extract a release, for example:

cvs export -r Release_1 prog2dir

▪ this will extract the source files that were frozen with the
given tag
o example of exporting a release, note that the deleted file
"makefile" is in Release_1, since it was removed after Release_1
was tagged::
o ==> mkdir ~/release1
o ==> cd ~/release1
o ==> cvs export -r Release_1
prog2dir
o cvs export: Updating prog2dir
o U prog2dir/f1.c
o U prog2dir/f2.c
o U prog2dir/makefile
o U prog2dir/makefile2
o U prog2dir/prog2.c
o U prog2dir/prog2.h
o ==> ls
o prog2dir
o ==> ls prog2dir
o f1.c f2.c makefile makefile2
prog2.c prog2.h
o ==> _

o log - display log entries, for example:

cvs log prog2.c

▪this will display all log entries for "prog2.c" in repository
o example of displaying log entries::
o ==> cd ~/sandbox/prog2dir
o ==> cvs log prog2.c
o

o RCS file:
/home/lczegel/cvsroot/prog2dir/prog2
.c,v
o Working file: prog2.c
o head: 1.2
o branch:
o locks: strict
o access list:
o symbolic names:
o Release_1: 1.2
o start: 1.1.1.1
o vendor-tag: 1.1.1
o keyword substitution: kv
o total revisions: 3; selected
revisions: 3
o description:
o ----------------------------
o revision 1.2
o date: 2007-03-09 18:59:12 -0500;
author: lczegel; state: Exp;
lines: +1 -1; commitid:
497b45f1f4d04567;
o Added a comment
o ----------------------------
o revision 1.1
o date: 2007-03-09 18:42:33 -0500;
author: lczegel; state: Exp;
commitid: 48d345f1f0e94567;
o branches: 1.1.1;
o Initial revision
o ----------------------------
o revision 1.1.1.1
o date: 2007-03-09 18:42:33 -0500;
author: lczegel; state: Exp;
 lines: +0 -0; commitid:
48d345f1f0e94567;
o Import source files
o

====================================
====================================
=====
o ==> _

o release - release a module after installing changes, for example:

cvs release prog2dir

▪this will check for any changed files that have not been
committed
▪ it will also remove all files in the sandbox if "-d" option is
used
o example of releasing a module:
o ==> cd ..
o ==> ls
o prog2dir
o ==> cvs release -d prog2dir
o M prog2.c
o You have [1] altered files in this
repository.
o Are you sure you want to release
(and delete) directory `prog2dir': y
o ==> ls
o ==> _