Version Control & Design Repositories

One of the greatest strengths of an electronic authoring and editing environment is the ease with which you can create and modify a file. This capability means that ideas can be captured, explored and matured quickly, but it also means that it can be difficult to keep track of changes made to valuable files such as source code and electronic design data.

The need to keep track of changes made to a file, combined with the need for a systematic solution for managing source captured in an electronic form, has given rise to Version Control Systems (VCS). Version control systems are software tools that are not only able to maintain a history of the various versions of a file, they also support opening any revision of that file, as well comparing changes made between any two versions of the file. A VCS will generally integrate with the local Operating System (OS) by providing additional versioning functions and operations for folders and files.

Version Control Systems can be operated completely independently of the authoring and editing environment used to create a file. They offer an interface that allows you to place (or 'check') files into a central storage area called the repository, a check-out feature to copy a file from the repository to a working folder, an update feature to check back in any changes to the repository, and a method of logging information about a change. These features are also included in Altium Designer itself.

Typically a version control system will also handle the situation where a file has been checked-out and modified by multiple people, who could then check their changes in on top of each other, potentially losing someone's work from the latest revision. Dealing with this requires tools to compare versions of the file to detect differences, and an interactive tool to merge the differences back into a single version of the file, such as Altium Designer's Collaborate, Compare and Merge capabilities for PCB design documents.

It is helpful to understand the terminology used with version control systems. Even though there are numerous systems available, they generally all use similar terms to describe their functionality.

Version Control Essentials

The basic approach to working with a version control system is to take a copy of, or 'check-out', the project files that you want to work on, from the repository into a working folder. These can then be modified and saved in Altium Designer, and when you decide it is appropriate, the updated files can be 'committed', or checked back in to the VCS repository. Check-out and check-in (commit) is performed through a version control system interface, which Altium Designer has built into its Storage Manager panel and Projects panel.

The key to how a version control system works is that it monitors the status of files that have been checked-out of the central repository. This means that the VCS knows that a file has been checked-out into your working folder, what revision was checked-out, and if it has been modified since it was checked-out. Each VCS uses its own approach to monitoring files, refer to the specific VCS documentation if you need further information.

Simple diagram of how Altium Designer interfaces to a Version Control System (VCS)

The figure above illustrates the concept of a VCS repository that holds a sequence of design file revisions (up to revision 5), with the latest copy checked out in the working folder. When the file in the working folder is opened in the Altium Designer environment, Altium Designer recognizes that the project file is under version control, with its current version control status being shown in both the Storage Manager and Projects panel.

Altium Designer's built in Version Control interface can be accessed directly from the Projects panel or from the Storage Manager panel, where more option are available.

The right-click menu in the Storage Manager panel (and the Projects panel) allows you to a perform standard VCS actions, such as checking back in a changed file. When you right-click and select Commit the VCS takes a copy of the file from the working folder, increments the revision number (stored internally in the VCS), and stores the copy of the file in its repository, along with a log message that you can enter to describe the changes made to the file. Most VCS systems do not store the entire file with every commit, instead they store the differences from the previous version.

Version Control installations

Altium Designer allows for three main approaches to interfacing with a Version Control System, all of which are configured in the Data Management - Version Control page of the Preferences dialog (DXP » Preferences). Altium Designer's interface can be configured to work with the following VCS applications:

• Altium Designer's internal copy of the Subversion (SVN) version control system.
• An external installation of the Subversion (SVN) version control system.
• An external installation of the Concurrent Versions System (CVS) version control system.
• The Altium Vault's built in Subversion (SVN) system, when using a centralized version control approach to access both vault-based and external Design Repositories – see Vault VCS Repository, below.

The most common and recommended approach is making use of the SVN system included with Altium Designer, which is enabled by selecting the Use built-in Subversion option in Preferences. Note that the actual SVN system executables are located in the \Subversion Client folder of the Altium Designer installation.

Use the SVN application supplied with the Altium Designer installation (recommended), or direct the VCS interface to an 'external' CVS or SVN system installed on the local machine.

Alternatively, where a compliant company SVN or CVS system is already available (its application is locally installed), the external connection options in the Version Control preferences are used to locate and apply its main executable(s).

Multiple user access

There are essentially two different approaches to providing multiple team members with access to the same set of files that are under Version Control. Depending on the VCS that is in use, you can either:

• Allow multiple check-outs (referred to as the unreserved check-out model). Note that if necessary, a file can be manually locked by a user, which will prevent other users committing a new version to the repository.
• Restrict file access to one person at a time (referred to as the lock-modify-unlock, or the exclusive check-out model)

Allowing multiple check-outs is the ideal approach as it allows different team members to continue working independently, without having to wait for someone else to check a file back in before they can work on it. However, it does require that the tools and techniques are available to resolve the inevitable situation where two people have modified the same file. When these capabilities are available, the foundation is in place for true multi user design collaboration and its associated benefits.

To support this situation, Altium Designer includes schematic and PCB comparison (or 'diff') capabilities, available through the Storage Manager and Collaborate, Compare and Merge panels. Altium Designer offers sophisticated PCB design collaboration features that allow file merge differences to be viewed and resolved within the editor, to ultimately create a new Head revision in the VCS. The advanced collaboration functionality also allows for live design collaboration between multiple users, with the ability to define and assign sections of a design as user Work Regions.

– See Collaborative PCB Design for more information on multiple user design collaboration.
– See Using Version Control for a guide to applying version control to project design in Altium Designer.

VCS Repositories

Before using version control, the project files must be recognized by both the VCS and Altium Designer as being under version control. This process can be different for the various VCS methods and applications, but it essentially entails creating and/or connecting to a design repository and adding design project files to that repository.

Design repositories are based on a database structure, and internally store information in a hierarchy of files and directories, referred to as a file tree. The actual repository that you connect can be an existing company 'central' design repository, or one you have created in an accessible location such as on the local PC or a shared network location.

Depending on the type of repository, it will be accessible via a range of protocols that include:

• Conventional file access, which is usually for local or network -based repositories.
• The svn protocol to a server-based repository, using plain text or TCP/IP.
• The http method to a server-based repository, generally using WebDAV over http.

VCS repositories are connected to, and created when necessary, in the Data Management – Design Repositories page of the Preferences dialog (DXP » Preferences).

Connect to a Repository

To connect to an existing SVN design repository for example, use the button to open the SVN Design Repository dialog. This provides Properties settings that allow you to define the name of the repository connection and its target folder path for checked out design files.

Locate an existing VCS repository to be registered in Altium Designer, and therefore be available for including design files under version control.

The dialog's Repository options need to be configured to match the available repository's location, an optional subfolder target, and a compatible protocol method for the connection. Note that the svn and http access methods require additional information that relates to the host server and its access.

For more information, see:

– The Data Management – Design Repositories page of the Preferences dialog.
– The SVN Design Repository dialog page.

Create a Repository

To create a local SVN design repository, go to the Data Management – Design Repositories page of the Preferences dialog (DXP » Preferences), and use the  button to open the Create SVN Design Repository dialog.

The dialog provides a range of configuration options that allow you to define the repository's folder location and method (connection protocol), and the local connection name and target folder path for checked out design files. Note that the svn and http access methods require additional information that relates to the host server and its access. For more information, see the above links.

Nominate or create a local folder that will be configured as a named VCS repository.

The installed VCS system will subsequently create the correct version control file structure and database in the nominated repository folder. Once created and registered, the new repository entry will be connected and listed in the Design Repositories page of the Preferences dialog. Click or to confirm the changes.

The process of creating a VCS repository – traditionally completed using an external (separate) VCS client – can be  done directly in Altium Designer's Preferences dialog.

With the new or existing design repository available to Altium Designer, project design files can be added to and retrieved (checked-out) from the repository using the Storage Manager and Projects panels, and commands from the main menu. As the repository files exist under version control, all design revisions are tracked and accessible from within Altium Designer.

Use the right click context menus in the Storage Manager or Projects panels to add a complete project folder (and its constituent design files) to version control, or add individual files as required. The design files under version control in the repository can be subsequently checked out and loaded in Altium Designer using the File » Check Out command, and ultimately Committed back to the repository (checked in) as new revisions when the edits are complete.

       
Once a compatible VCS repository is accessible in Altium Designer, design files can be added to (left dialog image) and checked out from (right dialog image) the repository.

Vault VCS Repository

As an alternative to conventional VCS repositories hosted locally or on the network, fully managed, a multi-user design repository can be created in the Altium Vault. Because of the Vault's tight integration with its VCS service (specifically SVN) and Altium Designer, user and client access can be centrally configured through common credentials.

This approach allows an organization to allocate multiple Vault-based design repositories to groups of users, who simply use their standard Vault sign-in credentials to access the Vault and any assigned VCS repositories. All Vault-based repositories are centrally configured through the vault's browser-based interface (see the ADMIN » VCS page), thereby simplifying the task of managing multiple version controlled repositories that have different client access requirements.

Additional information

Version Control Terminology

References