Introductory Concurrent Version System (CVS) UCR Technical Seminar 10/23/03 Dan Berger

Adgenda Introduction –What is configuration management? –Key concepts. CVS Workflow –Copy-Modify-Merge Getting Started with CVS –Creating a repository –Importing assets –Checking in & Checking Out Using CVS –Managing Change

Introduction: What is CM? Record Keeping –What assets (source, binary) went into producing some product? –What did this asset look like at some point in the past? Collaboration –Who's working on which assets? –Who worked on this asset last? –Who made a specific change to this asset (and when?)

Introduction: Key Concepts Repository: The “master” copy of the assets. –Contains all revision history for all assets. Working Directory (aka sandbox): a developers private copy of the assets. –Contains a copy of a particular version of assets.

CVS Workflow CVS allows multiple people to be working on the same set of assets at the same time. Copy-Modify-Merge means you take a copy of the assets, modify your local copy, and merge your changes back in to the master repository.

CVS Workflow (cont.) cvs checkout –edit to your hearts content… cvs update –resolve conflicts cvs commit

Getting Started w/ CVS Creating a Repository (one time only) Importing Assets Checking out a working copy Viewing changes Committing changes Working with previous versions

Creating a Repository % export CVSROOT=~/CVSRoot % cvs init % ls –l ${CVSROOT} drwx CVSROOT/ There are some magic files in ${CVSROOT}/CVSROOT – ignore them for now.

Importing Assets importing places a copy of an existing directory tree (rooted at `pwd`) into the repository cvs import mod-path vendor release –mod-path is the directory under $CVSROOT to import the files into –vendor and release are more complicated but (for our purposes) less important. I suggest vendor=`whoami`, release=“initial”.

Importing Assets Example % cvs import cvs-seminar/hello- world\ `whoami` initial \ –m “initial import” N cvs-seminar/hello-world/hello.C N cvs-seminar/hello-world/Makefile No conflicts created by this import

Importing Assets (Cont.) Importing assets doesn’t touch the files in the current directory. That also means changes to the files in the working directory aren’t tracked. We need to get a copy from the repository first…

Getting a Working Copy % cvs checkout \ cvs-seminar/hello-world cvs checkout: Updating cvs-seminar/hello-world U cvs-seminar/hello-world/Makefile U cvs-seminar/hello-world/hello.C % ls –l cvs-seminar/ CVS/ % ls –l cvs-seminar/hello-world CVS/ hello.C Makefile

Viewing Changes Imagine we changed the files – fixing the typo in hello.C and adding a default target to the Makefile. Before we commit these changes, we’d like to see what we actually changed: cvs can show us which files have changed, and/or the specific changes to the files.

cvs -n update % cvs –n update cvs update: Updating. M Makefile M hello.C ? hello the leading “M” indicates the file has been Modified. The “?” means the file isn’t being managed by CVS.

cvs diff % cvs diff hello.C Index: hello.C ========================================= RCS file: … retrieving version diff –r hello.C 11c11 < cout << “Helllo, world!” << endl; --- > cout << “Hello, world!” << endl;

cvs status cvs status will tell you the status of a file in your working copy. % cvs status hello.C =================================== File: hello.C Status: Up-to-date Working revision: x.x Repository revision: x.x …

Adding Files CVS will essentially “ignore” new files, until you tell it they’re important and should be managed. % cvs add README cvs add: scheduling file ‘README’ for addition cvs add: use ‘cvs commit’ to add this file permanently

Deleting Files first, remove the file from your working copy (with rm), then % cvs delete file cvs remove: scheduling `FILE’ for removal cvs remove: use ‘cvs commit’ to remove \ this file permanently % cvs commit Removing FILE; …/FILE,v <-- FILE new revision: delete; previous revision: 1.1 done

Removing Files (cont.) CVS doesn’t actually remove the file, it places it into the Attic. –You can still retrieve any version of the “deleted” file: % cvs up –r X.Y FILE U FILE

Renaming One place where CVS makes life difficult*. Renaming files is non-trivial. Two methods: –one that preserves change history, but requires file system access to the repository, –and one that breaks change history but can be done completely through the client.

Renaming: The Easy Way % cp old-name new-name % rm old-name % cvs delete old-name % cvs add new-name % cvs commit You can explain the rename in the log message, and point viewers to the old- name for complete revision history.

Committing Changes Once we’re happy with our changes, we need to commit them to the repository. We can commit all our changes, or changes to an individual file (often dangerous).

Checking In Example % cvs commit cvs commit: Examining. Checking in Makefile; …/Makefile,v <-- Makefile new revision 1.2; previous revision 1.1 RCS file: …/README,v done Checking in README: …/README,v <-- README initial revision 1.1 done Checking in hello.C …/hello.C,v <-- hello.C new revision 1.2; previous revision 1.1 done

Working with Versions the –r tag can be provided to CVS commands, and it will cause them to affect a specific version of the named asset. For example: % cvs diff –r 1.1 Makefile You can also check out previous versions of files ( cvs co –r x.x filename ), and even commit to (branch from) previous versions of files.

Diff and Patch Not strictly CVS related, but terribly valuable tools. diff generates the differences between two (sets of) files. patch can apply that set of differences to another file

Diff Example Say I have two copies of my project: –unmodified-copy and modified-copy % diff –Naurw unmodified-copy \ modified-copy CVS will do this also, without having two versions checked out: % cvs diff –auw –r other-version

Patch Example Once I have a unified diff (the –u to diff), I can apply the changes specified in the diff to another file: % patch < diff-file This also works with trees of files. Read the man page to patch for more options.

CVS Version Numbers Imported files have an initial version of – there’s a reason, but for now just ignore it. “Normal” version numbers are w.x – cvs automatically increments x each time you commit changes to the file. It never automatically increments w. –If you branch a file, it’s version number becomes w.x.y.z. We’re not going to talk about branches in this talk. (Advanced CVS, anyone?)

CVS Magic Strings Some strings have special meaning to CVS, and if they appear in your files, CVS will “evaluate” them during checkout. –$Id:$ is the most common/useful, it gets evaluated to a string of the form: $Id: Makefile,v /10/20 \ 23:08:20 dberger Exp $

CVS and Binary Files CVS assumes that files are text unless told otherwise. This can cause issues if a binary file (like a jpg, PDF, etc.) contains one of the magic strings mentioned above. This can be handled two ways: file-by-file, or by file extension: % cvsadmin –kb file or adding the extension to cvswrappers (more later)

${CVSROOT}/CVSROOT CVSROOT/ contains control files – many of which are only interesting if you’re using CVS in a group. –CVSROOT is just another module – so you can check it out/diff it/commit to it. –DON’T TOUCH THESE FILES DIRECTLY! Remember “cvswrappers”? It lives here – it allows hooks to run when files go in or out of CVS. There’s a sample linked from the tech seminar page.

Accessing CVS Remotely Three methods, pserver, rsh, ext. pserver is a cvs-specific network protocol, it’s not encrypted and has to be setup by the remote admin – so we’re going to ignore it. rsh is just too horrible for words, which leaves ext: % export CVS_RSH=ssh % export CVSROOT= \ note that cvsroot is the directory containing CVSROOT/

Remote CVS (cont.) Note that if your CVS repository is NFS exported and always available directly (I.e. it’s in your home directory), you don’t need to use the ext method to reach it. % export CVSROOT=/home/…/CVSRoot

What We Didn’t Cover cvs watchers and editors anonymous cvs CVS and IDE’s (emacs/eclipse, etc) Permissions Tagging Branching Merging Detecting and Resolving Conflicts …

Subversion a “better” CVS You can’t set it up for yourself (it’s repository can’t live on an NFS share, like your home directory). The command line interface is very similar (intentionally).

Where to Find More CVS Home Page: CVS Online Book: CVS GUI’s: –TortoiseCVS (Windows Explorer Extension): Subversion Home Page: Subversion Online Book (draft): bean.comhttp://svnbook.red- bean.com