Git Rebase: Rewriting History

Merge vs Rebase

Both merge and rebase integrate changes from one branch into another, but they do it differently:

Merge: Creates a merge commit

        main: A ─── B ─── C ─── M (merge commit)
                     \         /
        feature:      D ─── E

Rebase: Replays commits on top

        Before rebase:
        main:    A ─── B ─── C
                       \
        feature:        D ─── E
        After rebase:
        main:    A ─── B ─── C
                               \
        feature:                D' ─── E'

The commits D and E are replayed on top of C, creating new commits D' and E'.

When to Use Rebase

Basic Rebase

# On your feature branch
git checkout feature
git rebase main
This replays your feature commits on top of main

Interactive Rebase

Interactive rebase (-i) lets you edit, reorder, squash, or drop commits:

git rebase -i HEAD~3    # Edit last 3 commits

This opens an editor showing:

pick abc1234 Add login form
pick def5678 Fix typo in login
pick ghi9012 Add validation
Commands:
p, pick = use commit
r, reword = use commit, but edit message
s, squash = combine with previous commit
d, drop = remove commit

Common use: Squash commits

pick abc1234 Add login form
squash def5678 Fix typo in login
squash ghi9012 Add validation

⚠️ The Golden Rule

Never rebase commits that have been pushed to a shared branch.

Rebasing rewrites history. If others have based work on the original commits, rebasing will cause conflicts and confusion.

# SAFE: Rebase your local feature branch
git checkout my-feature
git rebase main
DANGEROUS: Rebase main (shared branch)
git checkout main
git rebase feature    # DON'T DO THIS!

Summary