Software Development Using CVS, ACM Mumbai - 09^th Nov, 2001

Roadmap

What is version control ?
Why version control ?
How CVS evolved ?
How to use it ?
Example project

What is version control ?

Keeping old versions of program.
Keeping track of these versions.
Manipulation of these versions.

Why version control ?

Scenario	: single user single project
Problem	: loss of older versions/snapshots

Scenario	: multiple user single project
Problem	: concurrent updation of a file

Why version control ? (contd..)

Encourages documentation of changes, change log.
Easy to manage parallel development of different versions of a file.
Regulates multiple developers wanting to change the same file.

How it evolved ?

Initial CVS shell scripts were written by Dick Grune.
Developed on newsgroup (comp.sources.unix, vol-6, december-1986).
Current version uses very small part of the original.
Brian Berliner redesigned and coded CVS (1989).
Jeff Polk later helped Brian (module and vender branch support).

How it evolved ? (contd..)

CVS is based on RCS (Revision Control System).
RCS was designed by Walter Tichy (1982).
Designed for maintaining revisions of documents, drawings, forms, articles, source code.
Other version control systems - AT&T's SCCS, IBM's CLEAR/CASTER, DEC'S CMS.

Environment Setup

CVSROOT - location of repository (contains protocol, username, server, path-to-cvsrootdir)
CVS_RSH - remote shell command to use when starting a cvs server.
CVSEDITOR - editor to use for recording log messages (during commit).
CVSREAD - makes the files in the working directory read-only (during checkout and update).

Anonymous User Commands

Logging in
$ cvs -d:pserver:anoncvs@subversions.gnu.org:/cvsroot/vm login
Checking out
$ cvs checkout module/file/dir
Updating
$ cvs update

Anonymous User Commands (Contd..)

Status indication letter for each file in the working directory :
U, P, A, R, M, C, ?
Some command modifiers :
$ cvs -z3 update -d
$ cvs -z3 update -l
$ cvs -z3 -n update -d

Developers Commands

Comitting
$ cvs commit [files..]
$ cvs commit -m "log message" [files..]
Adding/removing files
$ cvs add [files..]
$ cvs remove [files..]
Creating patches
$ cvs diff -u> my_cvs.patch
Version numbers
$ cvs commit -r 3.0

Repository Management Commands

Creating a repository
$ cvs -d /var/lib/cvs init
Importing a project
$ cvs project/pilot pilot-team start
Managing modules
$ cvs co CVSROOT/modules

pilot project/pilot

$ cvs co pilot

Repository Management Commands (contd..)

Revisions
$ cvs commit -r 3.0
Tags
$ cvs tag rel-1-0 .
$ cvs checkout -r rel-1-0 modulename

Repository Management Commands (contd..)

What to tag
$ cvs tag -c rel-1-0 .
$ cvs tag -r 1-0 rel-1-0 modulename
$ cvs tag -D date-spec rel-1-0 modulename
Deleting, moving, renaming tags
$ cvs tag -d rel-1-0 .
$ cvs tag -r 1-6 -F stable modulename

$ cvs tag -r old-tag-1-0 rel-1-0 modulename
$ cvs tag -d old-tag-1-0 modulename

Repository Management Commands (contd..)

Creating a branch
$ cvs tag -b rel-1-0-patches
$ cvs rtag -b -r rel-1-0 rel-1-0-patches modulename
Accessing branches
$ cvs checkout -r rel-1-0-patches modulename
$ cvs update -r rel-1-0-patches modulename

Repository Management Commands (contd..)

Branches and revisions

				    +-------------+
		Branch 1.2.2.3.2 -> ! 1.2.2.3.2.1 !
				    +-------------+
				   /
				  /
			+---------+    +---------+    +---------+
	Branch 1.2.2->  ! 1.2.2.1 !----! 1.2.2.2 !----! 1.2.2.3 !
			+---------+    +---------+    +---------+
		      /
Main trunk          /
	+-----+    +-----+    +-----+    +-----+    +-----+
        ! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 !
	+-----+    +-----+    +-----+    +-----+    +-----+
		   \
		    \	
		    +---------+    +---------+    +---------+
Branch 1.2.4 -> +-- ! 1.2.4.1 !----! 1.2.4.2 !----! 1.2.4.3 !
		    +---------+    +---------+    +---------+

Repository Management Commands (contd..)

Merging an entire branch

    +-----+    +-----+    +-----+    +-----+
    ! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !      <- The main trunk
    +-----+    +-----+    +-----+    +-----+
			!
			!
			!   +---------+    +---------+
	Branch R1fix -> +---! 1.2.2.1 !----! 1.2.2.2 !
			    +---------+    +---------+

$ cvs checkout modulename
$ cvs update -j R1fix file.c
$ cvs commit -m "Included R1fix"

OR (better approach)

$ cvs checkout -j R1fix modulename
$ cvs commit -m "Included R1fix"

Repository Management Commands (contd..)

Merging from a branch several times

	+-----+    +-----+    +-----+    +-----+    +-----+
	! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 !   <- The main trunk
	+-----+    +-----+    +-----+    +-----+    +-----+
		       !                           *
   		       !                          *
		       !   +---------+    +---------+    +---------+
      Branch R1fix -> +--- ! 1.2.2.1 !----! 1.2.2.2 !----! 1.2.2.3 !
		           +---------+    +---------+    +---------+

$ cvs update -j 1.2.2.2 -j R1fix file.c

$ cvs update -j R1fix:yesterday -j R1fix file.c
(specify the date last merge was done.)

$ cvs update -j merged_from_R1fix_to_trunk -j R1fix file.c
(tag the R1fix branch after every merge then use tag for every subsequent merge.)

Repository Management Commands (contd..)

File Status
$ cvs -n -q update
Several developers simultaneously attempting to run CVS
[11:43:23] waiting for bach's lock in /usr/local/cvsroot/foo

Informing other developers

	# file - CVSROOT/modules

	modulename -i prog -a first-dir

References

CVS Home (online manual - http://www.nongnu.org/cvs/).
Jan Barsodi's articles on CVS (http://zez.org/article/author/view/26/).

Other Stuff

Software Development Using CVS, ACM Mumbai - 09th Nov, 2001

Roadmap

What is version control ?

Why version control ?

Why version control ? (contd..)

How it evolved ?

How it evolved ? (contd..)

Environment Setup

Anonymous User Commands

Anonymous User Commands (Contd..)

Developers Commands

Repository Management Commands

Repository Management Commands (contd..)

Repository Management Commands (contd..)

Repository Management Commands (contd..)

Repository Management Commands (contd..)

Repository Management Commands (contd..)

Repository Management Commands (contd..)

Repository Management Commands (contd..)

References

Software Development Using CVS, ACM Mumbai - 09^th Nov, 2001