Merging

Merging takes changes from one branch and adds them to another. Think of it like two people editing the same document:

• You edit chapters 1-3, your colleague edits chapters 4-6
• You merge your changes into one complete document

# First, switch to the branch you want to merge INTO
git switch main

# Then merge the feature branch INTO main
git merge feature-login

A fast-forward merge happens when the target branch hasn’t changed since you branched off. Git simply moves the pointer forward.

gitGraph
   commit id: "Setup"
   commit id: "Homepage"
   branch feature-nav
   checkout feature-nav
   commit id: "Navigation bar"
   commit id: "Nav styles"
   checkout main
   merge feature-nav id: "Fast-forward"
   commit id: "Footer"

Before merge:

main ──▶ A ──▶ B
                  ▲
           feature-nav (pointing to B)

After fast-forward merge:

main ──▶ A ──▶ B
                ▲
           main & feature-nav (both at B)

git switch main
git merge feature-nav
# Updating a1b2c3d..f6e5d4c
# Fast-forward

Result: No new merge commit is created. The history stays linear.

A 3-way merge happens when the target branch has also moved forward since you branched off.

gitGraph
   commit id: "Setup"
   commit id: "Homepage"
   branch feature-nav
   checkout feature-nav
   commit id: "Navigation"
   checkout main
   commit id: "Footer"
   checkout feature-nav
   commit id: "Nav styles"
   checkout main
   merge feature-nav id: "Merge commit"
   commit id: "Deploy"

Before merge:

main:     A ──▶ B ──▶ C

feature:  A ──▶ B ──▶ D ──▶ E

After 3-way merge:

main:     A ──▶ B ──▶ C ──▶ F (merge commit)
                  \         /
                   D ───── E

git switch main
git merge feature-nav
# Merge made by the 'ort' strategy.
# (editor opens for a merge commit message)

Result: Git creates a merge commit with two parents — one from main, one from the feature branch. History shows both branches.

# 1. Setup
git init
echo "Initial" > file.txt
git add . && git commit -m "Initial commit"

# 2. Create and work on a branch
git checkout -b feature
echo "Feature work" >> file.txt
git add . && git commit -m "Feature commit"

# 3. Switch back and make changes on main
git checkout main
echo "Main work" >> file.txt
git add . && git commit -m "Main commit"

# 4. Merge feature into main
git merge feature
# (this will create a merge commit)

• Merging combines changes from one branch into another
• Fast-forward = simple pointer move (no new commit, clean history)
• 3-way merge = creates a merge commit when both branches moved forward
• Always switch to the target branch first (git switch main), then merge
• After merging, you can safely delete the feature branch