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Git Internals: How TinyGit Works

TinyGit is not just a wrapper around the git CLI; it implements core Git concepts in Python to demonstrate a deep understanding of version control internals.

The Object Model

Git is a content-addressable filesystem. TinyGit models this in src/git_objects/models.py.

1. Blobs (Binary Large Objects)

  • Purpose: Store file content.
  • Structure: blob <size>\0<content>
  • Python Class: BlobObject
  • Behavior: TinyGit reads raw bytes, but creates a wrapper that can hide content for binary files or large views to keep the UI clean.

2. Trees (Directories)

  • Purpose: Store directory structures and filenames.
  • Structure: A list of entries: <mode> <name>\0<sha1>
  • Python Class: TreeObject
  • Behavior: TinyGit parses the binary tree format using TreeObject.deserialize. It handles the recursive nature of Git trees (trees pointing to other trees).

3. Commits (Snapshots)

  • Purpose: Snapshot of a tree at a point in time, with metadata.
  • Structure: 
    tree <tree_sha1>
parent <parent_sha1>
author <name> <email> <timestamp>
committer <name> <email> <timestamp>

<message>
  • Python Class: CommitObject
  • Behavior: TinyGit builds the commit DAG (Directed Acyclic Graph) by linking CommitObjects via their parent_oids.

The DAG Builder (src/dag/builder.py)

To visualize the graph, TinyGit walks the commit history:

  1. Starts from references in .git/refs/heads (branches).
  2. Traverses parent pointers recursively.
  3. Topologically sorts commits to ensure children appear before parents (time flow).

API & Service Layer

  • GitService (src/api/service.py): The core logic. It orchestrates reading objects, updating HEAD, and effectively acts as the "Git command" runner.
  • main.py: A FastAPI application that exposes this logic to the React frontend.

Frontend Visualization

The React frontend uses react-force-graph-2d to render the DAG data provided by the backend, allowing for interactive exploration of the commit history.