Branch selection and branch specifier in Jenkins - Commands & Configuration

Introduction

When you want Jenkins to build code from a specific branch in your source control, you use branch selection and branch specifiers. This tells Jenkins exactly which branch to use for building and testing your project.

When you want to build the main branch to deploy the latest stable code.

When you want to test a feature branch before merging it into the main branch.

When you want to build a release branch for preparing a new version.

When you want Jenkins to automatically build pull requests from contributors.

When you want to run different jobs for different branches in the same repository.

Commands

This command updates the Jenkins job configuration with the specified YAML file that includes branch specifier settings.

Terminal

jenkins-jobs --conf jenkins.ini update my-job.yaml

Expected Output

Job my-job updated successfully

→

--conf - Specifies the Jenkins configuration file to use

Clones the repository locally to check available branches and verify branch names.

Terminal

git clone https://github.com/example/my-app.git

Expected Output

Cloning into 'my-app'...

remote: Enumerating objects: 10, done.

remote: Counting objects: 100% (10/10), done.

remote: Compressing objects: 100% (8/8), done.

remote: Total 10 (delta 1), reused 10 (delta 1), pack-reused 0

Receiving objects: 100% (10/10), done.

Lists all local and remote branches to find the exact branch name to specify in Jenkins.

Terminal

git branch -a

Expected Output

  main

  feature/login

  remotes/origin/HEAD -> origin/main

  remotes/origin/main

  remotes/origin/feature/login

Triggers a Jenkins job build specifying the branch 'feature/login' to build that branch's code.

Terminal

jenkins-cli build my-job -p BRANCH=feature/login

Expected Output

Started build #15 for job my-job with parameter BRANCH=feature/login

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-p - Passes parameters to the Jenkins job

Key Concept

If you remember nothing else from this pattern, remember: the branch specifier tells Jenkins exactly which branch to build from your source code repository.

Common Mistakes

Using an incorrect or misspelled branch name in the branch specifier.

Jenkins will fail to find the branch and the build will not start or will error out.

Always verify branch names with 'git branch -a' or your source control UI before specifying them in Jenkins.

Not updating the Jenkins job configuration after changing branch specifiers.

Jenkins will continue building the old branch and ignore your changes.

Update the Jenkins job configuration and reload or restart the job to apply new branch specifiers.

Summary

Use branch specifiers in Jenkins to tell it which branch to build from your repository.

Verify branch names with git commands before specifying them in Jenkins.

Trigger builds with parameters to select branches dynamically.