Intermediate 16 min

Branching and Merging

Work in parallel, merge, resolve conflicts and rebase.

What you will learn

Create and switch branches
Resolve a merge conflict
Choose merge vs rebase

A branch is an independent line of development. Branches let you build a feature or fix a bug without disturbing the stable code, then combine the work when it is ready. In Git, branches are extremely cheap: just a movable pointer to a commit.

git branch                     # list branches
git switch -c feature/login    # create AND switch to a new branch
# ...edit, commit...
git switch main                # go back
git branch -d feature/login    # delete a merged branch

HEAD is Git's name for "where you are now". Committing moves the current branch forward.

git switch main
git merge feature/login

Fast-forward: if main has not moved, Git just slides its pointer forward.
Merge commit: if both branches have new commits, Git creates a commit with two parents that joins them.

Merge conflicts

A conflict occurs when both branches changed the same lines. Git stops and marks the file:

<<<<<<< HEAD
const title = "Welcome";
=======
const title = "Hello there";
>>>>>>> feature/login

To resolve: open the file, choose or combine the correct code, delete the three marker lines, then finish.

git add src/app.js
git commit            # completes the merge
# changed your mind?  git merge --abort

Not scary

Conflicts are normal in team work. Small, frequent merges and pulling often keep them small.

Rebase

git rebase main replays your branch's commits on top of the latest main, producing a straight, linear history instead of a merge commit.

git switch feature/login
git rebase main          # re-apply my commits on top of main
git switch main
git merge feature/login  # now a clean fast-forward

Golden rule of rebasing

Never rebase commits that others have already pulled. Rebase rewrites history, which causes chaos for anyone who has the old version. Rebase your own local work freely.

Naming and habits

Prefix names by intent: feature/, fix/, chore/.
Keep branches short-lived: days, not months.
Keep main always working.

Try it yourself

Create a branch, change the same line of a file on both the branch and main, merge, then resolve the conflict by keeping both changes.

Show solution

echo "hi" > f.txt && git add f.txt && git commit -m "init"
git switch -c feature
echo "from feature" > f.txt && git commit -am "feature edit"
git switch main
echo "from main" > f.txt && git commit -am "main edit"
git merge feature       # CONFLICT
# edit f.txt to contain both lines, remove markers
git add f.txt && git commit