Storing and Managing Code with CVS

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Leonard Clark
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1 Storing and Managing Code with CVS One of the most important things you do, as a software developer, is version source code and other project files. What does it mean to version a file? According to Merriam Webster, a version is a variant or type of an original, and that s exactly what we mean in professional software development. In an iterative development process (like Extreme Programming) files undergo numerous changes during and after each iteration. Since code is owned by the team, everyone will need access to the latest version. In this handout we will examine a freely available open source tool for storing, sharing and managing code: CVS CVS, 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 late 1980 s. CVS was originally a command line tool, but many development environments such as NetBeans and Eclipse provide client-side user interfaces to access CVS repositories. CVS uses a client-server model to allow multiple users to access a code repository stored on a CVS server. This hand-out describes several common CVS operations using Eclipse as the client for accessing projects stored on the CVS server. To begin with, we assume that 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 to create a repository and this step is explained near the end of the handout. Information Required to Connect to the CVS Server The 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 CVS repository by following these steps 1. Change to Java Perspective (Window->Open perspective->java). Right click on the existing java project, and select Team->Share Project. cvsho435s05.01, Prepared by K. Gundamaraju & M. Wainer 1

server is selected and click next. 4. By default, the CVS module name is the same as the Eclipse project name. Check the Use an existing module radio button.

2 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 that Use Existing Repository location is checked and the repository location you entered earlier for CVS server is selected and click next. 4. By default, the CVS module name is the same as the Eclipse project name. Check the Use an existing module radio button. This will list the modules present in the current repository, select the module for your group and click next, like for example TTTx as shown in the figure below 5. In the select tag to synchronize with dialog box, make sure head is selected and then click next. cvsho435s05.01, Prepared by K. Gundamaraju & M. Wainer 2

3 2. In the Share Project resources window, expand the project tree and right click on build 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 and dist directory, to.cvsignore. Then Click Finish. The reason this is done is to prevent certain types of files from being stored on the repository. For instance, the dist directory holds information generated from other files so we don t want to waste 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 to say 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 the project you ve just made available on CVS. First of all, your co-worker needs to create a repository in CVS Repository Explorer view. Then she should following these steps (if she is checking out the project for the first time and she doesn t have any files in her local workspace) 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 to this repository. cvsho435s05.01, Prepared by K. Gundamaraju & M. Wainer 3

After checking out, the project will be created as a new Eclipse project. Since the local.

4 2. Select the module you are interested in, right click on it, and select check out as from the context menu. 3. In the check out as dialog, check the check out as a project in the workspace and change 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 the local.properties file is not stored in the repository, the first problem you ll encounter is that local class path variables which the project requires will not been defined. You will need to create the local.properties file (or modify from a team member s). Refer to the first 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 the repository then follow these steps (Your work will be overwritten with files from repository): 1. Select the project in the navigator view. Right click on it select Team->Share Project. Enter your user name and password. cvsho435s05.01, Prepared by K. Gundamaraju & M. Wainer 4

5 2. Right click on the project again and this time select Replace With -> Latest From Head. (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 can see the version and other information for the shared files. CVS label decorators indicate which files and folders are under CVS version control (a golden cylindrical icon decorating the resource s icon, indicating it s under version control),their current revision number, and whether they have been changed locally(a greater than sign indicating 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 Version Control) 2. Commit the file. (Right click on the file then select Team->Commit).Enter any comments in the Commit Dialog and click OK. Adding a file doesn t actually cause the file to appear in the CVS; it just sends a notification to CVS, which schedules the file for addition. The second step, committing the 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 the junit tests. You also need to make sure you don t overwrite other changes which may have been made since you checked out the file. See UPDATE below. You should also commit frequently work on small tasks and build up your software incrementally. Updating files from Repository: Refreshing your copy of code from the repository is called updating it. Right click the file, and select Team -> Update, and then resolve any conflicts (if you have changed the same lines that someone else has changed). Alternatively if you just want to replace your version with what s in the CVS repository, right click on the file/project and select Replace With -> Latest from Head. cvsho435s05.01, Prepared by K. Gundamaraju & M. Wainer 5

6 If you update and some of the changes conflict - Eclipse combines the changes in a single file that you need to edit by hand. This is a messy error prone process. It s more convenient 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 the synchronization issues for that file. Note the side by side comparison going on; here the local 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 navigate between changes. You can also use the two arrow buttons next to the navigation buttons to accept or make changes. The button with the left facing arrow copies the current change from the repository to your local code, and the button with the right facing arrow copies the current change from your local file to the repository. After you have synchronized your version of code with that in the repository, right click on the file name in the Synchronize view (if not open, then open it with Window->Open Perspective->Team Synchronizing View) and select Mark as Merged to indicate that you ve resolved the conflict. Commit the file by right clicking on either the file name or the 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 and resolve 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 the different versions and revisions of our files as well as any milestones we define and comment history we enter. To create a repository you need to know about the CVS server, the path of the CVS repository on it, and the protocol it is using. You also must have a valid username and password for the server or the repository. Follow these steps in Eclipse 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 Location cvsho435s05.01, Prepared by K. Gundamaraju & M. Wainer 6

7 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 CVS Disconnect is not like a logout. Disconnect is only used to disconnect a project from CVS, to disable the CVS operations that can be performed on the project and its resources 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 Confirm Disconnect 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

8 Some useful Tips: Never commit files with fatal compilation errors. Commit only after Update. (If you try to commit a file without updating it first you will sometimes get an error while performing the CVS commit. It says that Up- to-date check failed for the file. This is because the file you have locally is an old version and it is not in sync with the file in the repository. So first you have to update 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: Professional Java Tools for Extreme programming, 2004 Edition-Wrox publications Eclipse Cookbook Steve Holzner, O Reilly publications cvsho435s05.01, Prepared by K. Gundamaraju & M. Wainer 8

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