What is a Git Branch?

While my mental model visualizes a Git branch as a stack of building blocks, in actuality a Git branch is a pointer to a single commit.

How Can a Single Commit Represent a Branch

Since each commit points back to its parent (see What’s a Git Commit Parent), if we know the most recent commit (i.e. the top most block), we can trace our way back to determine the entire stack of blocks.

Under the Hood

Each branch is a text file stored in the hidden directory .git/refs/heads/.

After cloning my example Git branch with blocks repo. I can look at the file that represents the main branch with

less .git/refs/heads/main

This displays the following line (which is the commit hash for the commit at the tip of the main branch).

2b3a38be1df114556a019986dcfbfedda593925f

I can see the abbreviated version of this commit hash (2b3a38b) at the tip (top) of our branch when I run git log --oneline.

2b3a38b (HEAD -> main, origin/main) B
ec6a2c7 A

Sal Ferrarello (@salcode)

Sal is a PHP developer with a focus on the WordPress platform. He is a conference speaker with a background including Piano Player, Radio DJ, Magician/Juggler, Beach Photographer, and High School Math Teacher. Sal can be found professionally at WebDevStudios, where he works as a senior backend engineer.