Storing and Managing Code with CVS

Storing and Managing Code with CVSOne of the most important things you do, as a software developer, is version source codeand other project files. What does it mean to “version” a file? According to MerriamWebster, a version is a variant or type of an original, and that’s exactly what we mean inprofessional software development. In an iterative development process (like ExtremeProgramming) files undergo numerous changes during and after each iteration. Sincecode is owned by the team, everyone will need access to the latest version. In thishandout we will examine a freely available open source tool for storing, sharing andmanaging code: CVSCVS, the Concurrent Versioning System, is an open source versioning software system.CVS originated as UNIX shell scripts and was eventually rewritten as CVS in the late1980’s. CVS was originally a command line tool, but many development environmentssuch as NetBeans and Eclipse provide client-side user interfaces to access CVSrepositories.CVS uses a client-server model to allow multiple users to access a code repository storedon a CVS server. This hand-out describes several common CVS operations using Eclipseas the client for accessing projects stored on the CVS server. To begin with, we assumethat you have an existing Java project that you would like place into CVS. Furthermore,we assume that the CVS repository has already been created. Eventually you may need tocreate a repository and this step is explained near the end of the handout.Information Required to Connect to the CVS ServerThe following details are needed ( do not type { }s indicate your specific information )• Host : lab.cs.siu.edu• Repository path :/spare1/cvsroots/{repository name}• User/Password :{enter your Unix username / password}• Connection type : pserver• Leave Use Default Port checked.Putting an existing project into the repository:When your are ready to connect to the repository you can add your project to the CVSrepository by following these steps1. Change to Java Perspective (Window->Open perspective->java). Right click onthe existing java project, and select Team->Share Project.cvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 1

2. (Only in Linux systems) In the share project dialog select CVS and click next.3. In the Share Project with CVS Repository dialog box that appears, make sure thatUse Existing Repository location is checked and the repository location youentered earlier for CVS server is selected and click next.4. By default, the CVS module name is the same as the Eclipse project name. Checkthe Use an existing module radio button. This will list the modules present in thecurrent repository, select the module for your group and click next, like forexample TTTx as shown in the figure below5. In the select tag to synchronize with dialog box, make sure head is selected andthen click next.cvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 2

2. In the Share Project resources window, expand the project tree and right click onbuild directory and select Add to .cvsignore… option. Make sure the resource(s)by name option is selected and click OK. Similarly add, local.properties file anddist directory, to .cvsignore …. Then Click Finish. The reason this is done is toprevent certain types of files from being stored on the repository. For instance, thedist directory holds information generated from other files so we don’t want towaste space (and download time) by storing this in the repository.3. In the Commit Changes Dialog, click yes.4. In the Add the CVS Version control dialog, Click Yes.5. In the Commit dialog, enter a comment as prompted. There’s usually not much tosay the first time around, so Initial revision will suffice. And click OK.Checking out a project of CVS:Lets change our point of view for a moment and see how a co-worker would obtain theproject you’ve just made available on CVS. First of all, your co-worker needs to create arepository in CVS Repository Explorer view. Then she should following these steps (ifshe is checking out the project for the first time and she doesn’t have any files in her localworkspace)1. Expand the HEAD entry in the repository. Doing so shows CVSROOT directory(CVS’s administration directory) and any modules that have been checked in tothis repository.cvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 3

2. Select the module you are interested in, right click on it, and select check out asfrom the context menu.3. In the check out as dialog, check the check out as a project in the workspace andchange the project name to a different one if you wish to and click finish.After checking out, the project will be created as a new Eclipse project. Since thelocal.properties file is not stored in the repository, the first problem you’ll encounter isthat local class path variables which the project requires will not been defined. You willneed to create the local.properties file (or modify from a team member’s). Refer to thefirst lab handout (Core XP Practices with Java and Eclipse) to help solve any problems.You do the above steps if you are new to the project and want to check out the project.If you have some files already in your workspace and want to get the latest files from therepository then follow these steps (Your work will be overwritten with files fromrepository):1. Select the project in the navigator view. Right click on it select Team->ShareProject. Enter your user name and password.cvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 4

2. Right click on the project again and this time select Replace With -> Latest FromHead. (Head represents the main development path of the project.)3. In the Confirm Overwrite dialog, click OK.NOTE:Eclipse displays additional CVS information in the package explorer view, so you cansee the version and other information for the shared files. CVS label decoratorsindicate which files and folders are under CVS version control (a golden cylindricalicon decorating the resource’s icon, indicating it’s under version control),their currentrevision number, and whether they have been changed locally(a greater than signindicating the resource being changed locally) and the file type.To display the CVS label decorators, follow these steps:• Select Windows->Preferences.• Go to Workbench->Label Decorations• Check the CVS checkbox and click OK.Adding a new file to CVS:It takes two steps to check in a new file to CVS.1. Add the file to CVS.(Right click on the file then select Team->Add to VersionControl)2. Commit the file. (Right click on the file then select Team->Commit).Enter anycomments in the Commit Dialog and click OK.Adding a file doesn’t actually cause the file to appear in the CVS; it just sends anotification to CVS, which schedules the file for addition. The second step, committingthe file, causes the file to appear in the CVS Repository and be made available to others.NOTE:• It’s not a good idea to make changes and simply commit them in to CVS.Obviously, you should first make sure your changes compile and pass thejunit tests.• You also need to make sure you don’t overwrite other changes which mayhave been made since you checked out the file. See UPDATE below.• You should also commit frequently – work on small tasks and build up yoursoftware incrementally.Updating files from Repository:Refreshing your copy of code from the repository is called updating it. Right click thefile, and select Team -> Update, and then resolve any conflicts (if you have changed thesame lines that someone else has changed). Alternatively if you just want to replace yourversion with what’s in the CVS repository, right click on the file/project and selectReplace With -> Latest from Head.cvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 5

If you update and some of the changes conflict - Eclipse combines the changes in a singlefile that you need to edit by hand. This is a messy error prone process. It’s moreconvenient to perform merging using the Eclipse’s Synchronize Repository feature.1. Select the project in the Package Explorer and right-click on it.2. Select Team->Synchronize with Repository from the context menu.Then double click the file on the structure compare view to take a look at thesynchronization issues for that file. Note the side by side comparison going on; here thelocal file is compared to that of the repository. Lines appear connecting the differences.You can use the up and down arrow buttons in the Java Source Compare view to navigatebetween changes. You can also use the two arrow buttons next to the navigation buttonsto accept or make changes. The button with the left facing arrow copies the currentchange from the repository to your local code, and the button with the right facing arrowcopies the current change from your local file to the repository.After you have synchronized your version of code with that in the repository, right clickon the file name in the Synchronize view (if not open, then open it with Window->OpenPerspective->Team Synchronizing View) and select Mark as Merged to indicate thatyou’ve resolved the conflict. Commit the file by right clicking on either the file name orthe project name and selecting Commit. Enter a comment when prompted.Committing files to Repository (from local workspace):To commit files to repository select the individual files or the project.1. Right click on the resource (individual file/project) and select Team->Update.(To properly update you need to open the Team Synchronization perspective andresolve any conflicts before updating a file.)2. Again Right Click on the resource (individual file/project) and select Team->Commit.You should notice a change in the version numbers of the files updated.Creating a Repository:A code repository is a piece of software whose job is to keep track of our files, and thedifferent versions and revisions of our files as well as any milestones we define andcomment history we enter.To create a repository you need to know about the CVS server, the path of the CVSrepository on it, and the protocol it is using. You also must have a valid username andpassword for the server or the repository. Follow these steps in Eclipse 3.01. From the main menu select Window->Open perspective->Other.2. Select CVS Repository Exploring and click ok.3. In the CVS Repository view, right click and select New->Repository LocationcvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 6

4. Enter the following details• Host : lab.cs.siu.edu• Repository path :/spare1/cvsroots/{enter repository name}• User/Password :{enter your Unix username password}• Connection type : pserver• Leave Use Default Port checked.5. Click Finish.Disconnecting a project from CVSDisconnect is not like a logout. Disconnect is only used to disconnect a project fromCVS, to disable the CVS operations that can be performed on the project and itsresources and optionally to remove the CVS information (stored in the CVS folders)associated with the project. This might be done after a project due date for instance.To disconnect a project from CVS:1. In the Navigator view, select the project to be disconnected.2. Select Team > Disconnect from the project's pop-up menu. The ConfirmDisconnect from CVS dialog opens.3. In the dialog, click yes to disconnect the project.NOTE: Please don’t disconnect when the project is active.cvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 7

Some useful Tips:• Never commit files with fatal compilation errors.• Commit only after Update. (If you try to commit a file without updating it firstyou will sometimes get an error while performing the CVS commit. It says thatUp- to-date check failed for the file. This is because the file you have locally is anold version and it is not in sync with the file in the repository. So first you have toupdate your file locally before committing it)\• Once you have files on the local directories, never commit the whole project,commit the individual files separately.References:• http://www.eclipse.org/• Professional Java Tools for Extreme programming, 2004 Edition-Wroxpublications• Eclipse Cookbook – Steve Holzner, O’Reilly publications• https://www.cvshome.org/cvsHO435S05.01, Prepared by K. Gundamaraju & M. Wainer 8