DevOps, Git, Version Control Systems

How-to use Jenkins to keep your branches fresh


Although I prefer feature toggles over branching there can be instances that feature toggles are not practical. Think of a situation where you need to upgrade the underlying framework (or platform) of your application. Some examples from the Java world could be, newer JDKs, the latest Spring framework that contains breaking API changes, the new NetBeans platform that your desktop client is based on etc. etc.

In such situations when you have created a branch in your Git repo for development there is a risk that the master code base will diverge drastically from the branch. Therefore it is a good idea to keep your branch fresh by regularly merging ‘master changes’ into it. This not only saves you from having to resolve many conflicts when you perform a ‘big bang‘ merge, but it also ensures the functionality implemented in the master works in your branch more frequently.

Now you can do this manually by regularly merging master changes into your branch, but instead you can use Jenkins to easily automate the process. Since this can be scheduled to run frequently you will get faster feedback when a change in the master breaks your branch.

Here’s how you do it.

1: Setup a job that tracks both your master and dev branch under Source Code Management. Use the Additional Behaviours/Merge before build option to merge master changes into your branch.

jenkins_merge_branch1

In short, this would fetch master, merge into branch, build and (ideally) run all tests of your application.

2: Next use the Git publisher feature in the post build section to push your branch containing the merged changes to the remote Git repo.

jenkins_push_merge

You can perhaps schedule this job @hourly to ensure your branches stays fresh with master changes.

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