Branches in Git 관련

A Visual Guide to Git Internals — Objects, Branches, and How to Create a Repo From Scratch

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Many of us use git on a daily basis. But how many of us know what goes on under the hood? For example, what happens when we use git commit? What is stored between commits? Is it just a diff between the current and previous commit? If so, how

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A Visual Guide to Git Internals — Objects, Branches, and How to Create a Repo From Scratch

Many of us use git on a daily basis. But how many of us know what goes on under the hood? For example, what happens when we use git commit? What is stored between commits? Is it just a diff between the current and previous commit? If so, how

A branch is just a named reference to a commit.

We could always reference a commit by its SHA-1 hash, but humans usually prefer other forms to name objects. A branch is one way to reference a commit, but it’s really just that.

In most repositories, the main line of development is done in a branch called master. This is just a name, and it’s created when we use git init, making it is widely used. However, it’s by no means special, and we could use any other name we’d like.

Typically, the branch points to the latest commit in the line of development we are currently working on.

A branch is just a named reference to a commit

To create another branch, we usually use the git branch command. By doing that, we actually create another pointer. So if we create a branch called test, by using git branch test, we are actually creating another pointer that points to the same commit as the branch we are currently on.

Using git branch creates another pointer

How does git know what branch we’re currently on? It keeps a special pointer called HEAD. Usually, HEAD points to a branch, which in turns points to a commit. In some cases, HEAD can also point to a commit directly, but we won’t focus on that.

HEAD points to the branch we are currently on.

To switch the active branch to be test, we can use the command git checkout test. Now we can already guess what this command actually does — it just changes HEAD to point to test.

git checkout test changes where HEAD points

We could also use git checkout -b test before creating the test branch, which is the equivalent of running git branch test to create the branch, and then git checkout test to move HEAD to point to the new branch.

What happens if we make some changes and create a new commit using git commit? Which branch will the new commit be added to?

The answer is the test branch, as this is the active branch (since HEAD points to it). Afterwards, the test pointer will move to the newly added commit. Note that HEAD still points to test.

Every time we use git commit, the branch pointer moves to the newly created commit.

So if we go back to master by git checkout master, we move HEAD to point to master again.

Now, if we create another commit, it will be added to the master branch (and its parent would be commit B2424).