135.4 Branching and merging

Learn how branches help you work on features independently, and how to merge them safely into the main codebase.

What is a branch?

A branch is a separate line of development in a Git repository. It allows you to make changes without affecting the main version of your project.

Branches are commonly used to:

• Build new features

• Fix bugs

• Try out ideas

• Work on different tasks without interfering with each other

Every Git repository starts with a default branch called main.

You can create a new branch to work on something independently, then merge it back into main when it’s ready.

Why use branches?

Using branches keeps your main codebase clean and stable.

For example:

• You create a branch called feature-login

• You build and test the login feature

• Once it’s working, you merge it into main

If something goes wrong, the rest of your code isn’t affected.

This process also supports collaboration, as multiple team members can work on their own branches simultaneously.

How branching is done in Git for developing a new feature. A branch is the isolated and independent line of developing the feature. Assume the middle line as the master branch where the code is stable and updated. Then, assume a developer-1 is assigned to develop Feature – 1. Developer-1 is cutting a branch from the master branch (magenta colour). Developer-2 is assigned to develop Feature-2 and is cutting a branch from the master branch (blue colour).

In the Git graph above, Developer-1 is taking the branch from master to develop feature-1 (assuming File-1 and File-3 will be changed for development). Therefore, the developer can safely commit their changes to both files in the master branch.

Developer-2 is taking the branch from master to develop feature-2 (assuming File-2 and File-4 will be changed for development).

Branching in Git involves logically copying the codebase. When it is merged into the master branch, only the snapshot of the changes from the feature branch is appended to the master branch. In other version control systems, like SVN, branches are copied when cutting the branch and replaced when merging with the master branch.

Common Git branch commands

git branch                      # List all branches
git branch new-feature         # Create a new branch
git checkout new-feature       # Switch to that branch
git switch new-feature         # (Alternative modern command)
git merge new-feature          # Merge branch into current one

A typical branching timeline might look like this:

main:     A──B─────E────F
                 \     
feature:           C────D

• A and B are commits on main

• You branch off to feature, adding commits C and D

• When the feature is complete, you merge it back into main, creating commits E and F

Merging and merge conflicts

When you merge one branch into another, Git attempts to combine the changes automatically. If both branches edited the same part of a file, you get a merge conflict.

Git will mark the conflict in the file like this:

<<<<<<< HEAD
print("Hello from main")
=======
print("Hello from feature branch")
>>>>>>> feature

You must resolve the conflict manually, then add and commit the resolved file.

Example merge steps:

git checkout main
git merge feature-branch
# If there's a conflict:
# 1. Open the file and fix the conflict
# 2. git add resolved_file.py
# 3. git commit -m "Resolve merge conflict"

Deleting a branch

Once a feature has been merged, you can delete the branch:

git branch -d feature-branch

This keeps your workspace clean.

Summary

• A branch lets you work on a task without affecting the main project.

• You can merge branches once the work is complete.

• Merge conflicts happen when the same part of a file is changed in two branches.

• Branching and merging are essential for collaborative and safe software development.

In the next section, you’ll learn how to apply version control within a larger workflow, using Git to support Agile project development.