Systems & CLI · Advanced
Build Your Own Git
Reimplement the core of Git as a content-addressable store with init, add, commit, log, and branches backed by SHA-1 blobs, trees, and commits.
You rebuild the plumbing of Git from first principles, creating a .git-style directory and implementing the object model: blobs for file contents, trees for directories, and commits that point to a tree and parents. You hash and zlib-compress objects by their SHA-1, write them into the object store, build an index for staging, and implement init, add, commit, log, and lightweight branches and refs. It is worth building because Git's user interface is famously confusing until you see the simple, elegant data model underneath, after which the whole tool clicks. Implementing it teaches hashing, content-addressable storage, and the directed acyclic graph of commits, which is exactly the mental model strong engineers use to resolve real merge and history problems.
What you build
- Initializes a repository with an object store and refs
- Hashes file contents into SHA-1 blob objects
- Builds tree objects representing directory snapshots
- Creates commit objects linking trees and parent commits
- Stages changes through an index file
- Walks and prints history with a log command
- Creates and updates branches and HEAD refs
What it teaches
- Content-addressable storage and SHA-1 hashing
- Git's blob, tree, and commit object model
- The commit DAG and how history is traversed
- Index and staging-area mechanics
- Refs, HEAD, and branch pointers
- zlib compression and binary file formats
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Take it further
- Implement a diff between two trees or the index and working tree.
- Add a clone or fetch over the Git smart HTTP protocol.
- Implement a three-way merge with conflict markers.
