Git

Merge

You might say

The feature I built separately works. How do I bring it back into the main version?

Combine the commits from one branch into anotherMerge brings two lines of history together. Git can combine independent changes automatically, but overlapping edits may create conflicts that a person must resolve. Review the result and run tests after resolving, because a clean text merge can still break behavior.

main version

New Features

✓The main version has been updatedThe changes on both sides have been put together

git merge feature/new-nav

Merge brings the completed changes of another branch into the current branch. If both sides have changed the same place, Git will pause and ask you to decide what to keep in the end.

Anatomy

<<<<<<< HEAD <h1>Xiaoli's homepage</h1> ======= <h1>Xiaoli’s photography homepage</h1> >>>>>>> feature/new-nav

Starting here is the conflict area, HEAD refers to the version of the branch you are currently on.

What does this line look like on the current branch? It is usually the content of the main line.

The boundary between the upper and lower versions must be deleted together when resolving the conflict.

What does this line look like on the merged branch?

The conflict area ends here, marking which branch the content comes from.

Variants

Fast-forward

Updating a3f9c21..e7b2d48

The target branch has no independent new commits

Merge Commit

Merge made by the 'ort' strategy.

There are new commits on both sides and the merge node needs to be retained

merge --abort

git merge --abort

When you need to abandon the current unfinished merge

Typical use cases

Feature integration

zsh — my-first-page

$ git switch main Switched to branch 'main' $ git merge feature/new-nav Merge made by the 'ort' strategy. index.html | 24 ++++++++++++++----- 1 file changed, 16 insertions(+), 8 deletions(-)

Pull request merge

📄 index.html⚠ 1 conflict

<<<<<<< HEAD (main line)
<h1>Xiaoli’s homepage</h1>
=======
<h1>Xiaoli’s photography homepage</h1>
 feature/new-nav (branch)

Edit to the final content, remove all conflict tags and resubmit

Release preparation

📄 index.html Merge conflict

Adopt current changesAdopt incoming changesKeep changes from both parties

<h1>Xiaoli’s homepage</h1> (current · HEAD)
<h1>Xiaoli's photography homepage</h1> (incoming · branch)

You can choose to keep current changes, incoming changes, or both changes

Conflict resolution

New navigation bar #2

maya-lee wants to merge feature/new-nav into main

✓ This branch has no conflict with the base branch

Merge pull request

Click this green button on the web page, the effect is equivalent to git merge

Quick decision

Git merge vs rebase: which should you use?

Use Merge as the safer default for shared commits. Consider Rebase on an unshared personal branch when you want a linear history before review.

Decision point	Git Merge	Git Rebase
Commit history	Preserves true branch history and explicit merge commits (or fast-forwards the branch pointer).	Replays commits onto a new base, generating new commit hashes to produce a linear history.
Collaboration	Keeps existing commit IDs, making shared history easier to integrate.	Creates new commit IDs; rewriting shared history requires explicit team coordination.
When to use	Merging a feature into main or integrating a shared team branch.	Cleaning up an unshared personal branch or replaying it onto the latest main before review.