Branch selection and branch specifier in Jenkins - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a branch specifier in Jenkins?

A branch specifier tells Jenkins which branch to build from your source code repository. It helps Jenkins pick the right code version.

beginner

How do you specify the main branch in Jenkins using a branch specifier?

You use */main or */master in the branch specifier field to tell Jenkins to build the main branch.

intermediate

What does the asterisk (*) mean in a Jenkins branch specifier like */feature/*?

The asterisk (*) is a wildcard that matches any characters. So */feature/* matches any branch inside the feature folder or prefix.

beginner

Why is branch selection important in Jenkins pipelines?

Branch selection ensures Jenkins builds and tests the correct version of your code. It helps avoid mistakes like building old or wrong branches.

intermediate

How can you select multiple branches in Jenkins using branch specifiers?

You can enter multiple branch specifiers each on a separate line, like */main */develop, to build both branches.

What does the branch specifier */develop mean in Jenkins?

A Build the develop branch

B Build all branches

C Build the main branch

D Build no branches

The */develop specifier tells Jenkins to build the develop branch specifically.

Which symbol is used as a wildcard in Jenkins branch specifiers?

A #

B $

C *

D ?

The asterisk (*) is used as a wildcard to match any characters in branch names.

How do you specify multiple branches in Jenkins branch specifier?

A Enter each on a new line

B Separate with semicolons

C Use a single wildcard

D Use spaces

Multiple branch specifiers are entered each on a new line in the field.

Why should you carefully select branches in Jenkins builds?

A To save disk space

B To build the correct code version

C To speed up the internet

D To avoid using Jenkins

Selecting the right branch ensures Jenkins builds the correct version of your code.

What does */feature/* match in Jenkins branch specifier?

A Only main branch

B Only the feature branch

C No branches

D Any branch starting with feature/

The wildcard matches any branch that starts with feature/.

Explain how branch specifiers work in Jenkins and why they are useful.

Think about how Jenkins knows which code to build.

Describe how to select multiple branches for building in Jenkins using branch specifiers.

Consider how to tell Jenkins to build more than one branch.

Practice

1. What does the Branch Specifier field in Jenkins do?

easy

A. It tells Jenkins which branch or branches to build.

B. It specifies the build timeout duration.

C. It defines the build environment variables.

D. It sets the Jenkins user permissions.

Solution

1. Step 1: Understand the purpose of Branch Specifier

   The Branch Specifier is used to tell Jenkins which branch or branches to build from the source code repository.

2. Step 2: Eliminate unrelated options

   Timeout, environment variables, and user permissions are unrelated to branch selection.

3. Final Answer:

   It tells Jenkins which branch or branches to build. -> Option A

4. Quick Check:

   Branch Specifier = Select branch to build [OK]

Hint: Branch Specifier selects branches to build in Jenkins [OK]

Common Mistakes:

• Confusing branch specifier with build timeout
• Thinking it sets environment variables
• Assuming it controls user permissions

2. Which of the following is the correct syntax to specify the master branch in Jenkins Branch Specifier?

easy

A. refs/remotes/master

B. refs/tags/master

C. refs/heads/master

D. refs/branches/master

Solution

1. Step 1: Recall Git reference format for branches

   Branches in Git are referenced as refs/heads/branch-name. So the master branch is refs/heads/master.

2. Step 2: Identify incorrect references

   refs/tags/ is for tags, refs/remotes/ is for remote tracking branches, and refs/branches/ is not a valid Git ref.

3. Final Answer:

   refs/heads/master -> Option C

4. Quick Check:

   Branch refs start with refs/heads/ [OK]

Hint: Use refs/heads/branch-name for branch specifier [OK]

Common Mistakes:

• Using refs/tags/ instead of refs/heads/
• Confusing remote refs with local branch refs
• Using invalid refs/branches/ prefix

3. Given the branch specifier refs/heads/feature/*, which branches will Jenkins build?

medium

A. Only the branch named exactly 'feature/*'.

B. Only the 'master' branch.

C. All branches except those starting with 'feature/'.

D. All branches starting with 'feature/', like 'feature/login' and 'feature/ui'.

Solution

1. Step 1: Understand wildcard usage in branch specifier

   The asterisk (*) acts as a wildcard matching any characters after 'feature/'. So it matches all branches starting with 'feature/'.

2. Step 2: Analyze each option

   Only the branch named exactly 'feature/*'. is incorrect because it treats '*' literally. All branches except those starting with 'feature/'. is opposite meaning. Only the 'master' branch. is unrelated.

3. Final Answer:

   All branches starting with 'feature/', like 'feature/login' and 'feature/ui'. -> Option D

4. Quick Check:

   Wildcard * matches multiple branches [OK]

Hint: Use * wildcard to match multiple branches [OK]

Common Mistakes:

• Treating * as a literal character
• Assuming it excludes matching branches
• Confusing branch names with tags

4. You set the branch specifier to refs/heads/release but Jenkins builds no branches. What is the likely problem?

medium

A. The branch name is incorrect or does not exist in the repo.

B. The Jenkins server is offline.

C. The build script has syntax errors.

D. The workspace is full.

Solution

1. Step 1: Check branch existence

   If Jenkins builds no branches, the specified branch refs/heads/release might not exist in the repository.

2. Step 2: Rule out unrelated issues

   Server offline, build script errors, or workspace full would cause different errors or failures, not silent no build.

3. Final Answer:

   The branch name is incorrect or does not exist in the repo. -> Option A

4. Quick Check:

   Branch specifier must match existing branch [OK]

Hint: Verify branch exists before setting specifier [OK]

Common Mistakes:

• Assuming Jenkins server status causes no build
• Blaming build script syntax for branch selection
• Ignoring branch existence check

5. You want Jenkins to build all branches except those starting with hotfix/. Which branch specifier pattern should you use?

hard

A. !refs/heads/*

B. refs/heads/*, !refs/heads/hotfix/*

C. refs/heads/*

D. refs/heads/hotfix/*

Solution

1. Step 1: Understand inclusion and exclusion patterns

   Jenkins supports including all branches with refs/heads/* and excluding specific branches with !refs/heads/hotfix/*.

2. Step 2: Analyze options

   refs/heads/*, !refs/heads/hotfix/* includes all branches but excludes hotfix branches. refs/heads/hotfix/* only includes hotfix branches. refs/heads/* includes all branches without exclusion. !refs/heads/* excludes all branches.

3. Final Answer:

   refs/heads/*, !refs/heads/hotfix/* -> Option B

4. Quick Check:

   Use ! to exclude branches in specifier [OK]

Hint: Use ! prefix to exclude branches in specifier [OK]

Common Mistakes:

• Not using exclusion pattern with !
• Only specifying excluded branches
• Excluding all branches accidentally