A SVN branching strategy that works

Version control systems play a vital role in the success of a software development team. This blog aims to provide a simple branching and merging strategy to manage the code in a fast paced team development environment.

When do you need branching?

You may need to adopt branching in many different scenarios. Let us assume that on a day to day basis you use agile methodologies such as extreme programming or scrum and you have finally released a reasonably complex project with Version 1.0.0.0. Couple of days after the release, you get a request for a new feature that must go as Version 1.1.0.0. You envision it will take couple of weeks to get that feature coded, tested and released. Meanwhile, simple modifications and patches are requested on a day to day basis in the Version 1.0.0.0.

Essentially, with the changing business needs you are required to do a deployment every other day or so i.e. your deployment cycle is 2 days or less.

With a team of 10 developers it will be a nightmare in the absence of a proper branching strategy.

Trunk, branch, and tag are the 3 main divisions in subversion repository.

Trunk:
The code in trunk is always maintained as close to release state as possible. Any developer making changes to the trunk must be absolutely certain that his or her part can be coded, tested and is ready to deploy within 2 days (can vary depending on your length of deployment cycle). If it takes more than 2 days, they are not allowed to directly change the code in the trunk. They have to create a branch.

Branch:
Developer Branch:
Each developer must create his or her own branch if their code will take more time to program than your normal deployment cycle. It is the responsibility of the developer to regularly (timeframe depends on your development environment) merge changes from trunk to his branch.

Feature branch:
Create a feature branch if 2 or more developers are going to work on a new feature that will take considerable time to complete. It is the responsibility of the team lead to merge changes from trunk to this feature branch on a regular basis.

It is always beneficial to merge changes from trunk frequently. Because, after a couple of days conflict between trunk version and branch version can get out of hand and merging will practically be impossible.

When the developer branch or feature branch is ready for release, merge changes back from the branch to trunk.

Tags:
Tag is similar to branch. When you create a branch simply rename the folder from branch/branches to tag. I always use Tags to tag a release whenever a new release version is deployed. This will come in handy if a very minor patch has to be made on the release version when your trunk is temporarily dirty. Ideally, you do not merge from trunk to the tag.

Finally, remember that there is no ideal branching and merging strategy. It pretty much depends on your unique development environment. If you have any other strategy, I would like to hear about that.


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