Merging Branches

Merging integrates changes from one branch into another. Git automatically finds the common ancestor and combines changes. There are two main strategies: fast-forward (linear) and three-way merge (creates a merge commit).

01.Fast-Forward Merge

When the target branch (main) has no new commits since the feature branch was created, Git can simply move the pointer forward — no merge commit is needed. The result is a perfectly linear history. This is the default when possible and keeps history clean and readable.

Branch Visualization

main

feature

HEAD

02.Three-Way Merge

When both branches have new commits since they diverged, Git performs a three-way merge using: the tip of your current branch, the tip of the incoming branch, and their common ancestor commit. Git creates a new "merge commit" with two parents. Use --no-ff to always force a merge commit even when fast-forward is possible.

Commit Timeline

a1b2c3d

init

b2c3d4e

feat

c3d4e5f

fix

d4e5f6a

HEAD

Commands

commands — click to reveal output

git checkout main

First: switch to the branch you are merging INTO

git merge feature/login

Merge feature/login into current branch

▼ show output

git merge --no-ff feature/signup

Always create a merge commit (preserves branch history in log)

▼ show output

git merge --squash feature/wip

Squash all branch commits into one staged change to commit yourself

git merge --abort

Abort a merge that has conflicts (returns to pre-merge state)

git log --oneline --graph

Visualize merged history

▼ show output

KNOWLEDGE CHECK

When does a fast-forward merge happen?

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