In a developer team a version control system is usually not only used for keeping the version history but also to synchronize the work of the team members. A web-designer might do changes in style-sheet (.css) files and images, other team members might change the layout-files (.xml). All these files might belong to the same “screen”.
At development time it is very convenient to check-in/check-out single files. If only the complete .war file is checked-in/out, then only 1 team member can do changes at the same time.
For “frozen product versions” it might be different. Here you might additionally check-in the frozen product as a whole.
…about version control system integration:
How convenient the “check-in/check-out” is, is a matter of the version control system integration. Although multiple files are checked-in/checked-out it still can be just a single click.
Eclipse for instance has very good support for CVS. Using the Application Designer Plugins, Eclipse + CVS is one option. But there are others.
Independent of the version control system you are using: It is very important to check in the right files. I don’t recommend to check in the HTML-files! Application Designer generates these files and they depend on the Application Designer version.
The following files must be checked in:
Layout definition files (in the directory \xml), except the file ZZZZZGenerated.xml;
Help resources (underneath the directory \help);
Multi-language (internationalization) resources (underneath the directory \multilanguage);
Any other resources that you use in your layouts, such as images or styles.
Using for instance Eclipse+CVS you can simply use .cvsignore files to skip all other files and then check in a complete project.
Hope this helps,