Branches

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Branches#

A branch is a reference to a commit, and can be moved to some future commit. This page gives an overview of the tools git has to work with branches.

Overview#

This section provides an overview of the basics of dealing with branches in git:

  • git branch for listing available branches.

  • git branch <branch_name> for creating a new branch.

  • git checkout <branch_name> for switching between branches.

  • How a branch reacts to the creation of a new commit while HEAD refers to that branch.

We will consider the typical operations with git branches with the repository created in the following cell as example.

mkdir /tmp/branches_overview
cd /tmp/branches_overview
git init &> /dev/null

A newly created repository will only contain the master branch. The next cell shows the log of the repo after the first commit.

echo "some text" &> some_files
git add --all
git commit -m "first commit" &> /dev/null
git log --decorate

commit 96a988189f4be3526ff4e2bb4e48a192cd4f08c9 (HEAD -> master)
Author: fedor <kobfedsur@gmail.com>
Date:   Wed Jan 8 17:25:50 2025 +0300

    first commit

The following cell shows awailable branches by using git branch.

git branch

* master

There is only the main branch. The following code creates an extra branch, new_branch, and lists available branches.

git branch new_branch
git branch

* master
  new_branch

Now, in git log, you can see that both master and new_branch refer to the same commit. However, the syntax HEAD -> master indicates that the master branch is currently being used.

git log

commit 96a988189f4be3526ff4e2bb4e48a192cd4f08c9 (HEAD -> master, new_branch)
Author: fedor <kobfedsur@gmail.com>
Date:   Wed Jan 8 17:25:50 2025 +0300

    first commit

With git checkout new_branch you can set new_branch as the branch that HEAD points to.

git checkout new_branch
git log

Switched to branch 'new_branch'
commit 96a988189f4be3526ff4e2bb4e48a192cd4f08c9 (HEAD -> new_branch, master)
Author: fedor <kobfedsur@gmail.com>
Date:   Wed Jan 8 17:25:50 2025 +0300

    first commit

But what does HEAD -> new_branch actually mean? During a git commit, HEAD points to the new commit, and the branch it refers to moves along with it. The following cell creates a new commit and displays the resulting git log.

echo "hello" > new_file
git add --all
git commit -m "add new file" &> /dev/null
git log --all --graph

* commit 4a10dac0f6c48e7556e066a1348de4ef7b30719c (HEAD -> new_branch)
| Author: fedor <kobfedsur@gmail.com>
| Date:   Wed Jan 8 17:25:58 2025 +0300
| 
|     add new file
| 
* commit 96a988189f4be3526ff4e2bb4e48a192cd4f08c9 (master)
  Author: fedor <kobfedsur@gmail.com>
  Date:   Wed Jan 8 17:25:50 2025 +0300
  
      first commit

As a result, HEAD and new_branch, which HEAD referred to, have moved to the new commit.

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