@rehearse/git-core

Pure-TypeScript implementation of the git protocol. No native dependencies. Runs on Cloudflare Workers, Node, Bun, Deno, and the browser.

A complete-enough git for in-process work: parse and serialize objects, read and write packfiles, speak the smart-HTTP wire protocol, do diffs and three-way merges, manage refs. ~2.4k lines of source, 162 tests passing.

Used internally by @rehearse/runner to run actions/checkout and read repo state without shelling out to system git. Standalone-useful for any tool that needs to manipulate git objects in-process.

Install

npm install @rehearse/git-core

Single runtime dependency: pako for zlib (the git wire format and packfile encoding rely on it). Pure JS, no node-gyp.

What's inside

Module	Purpose
`objects`	Blob / tree / commit / tag parsing + serialization. SHA-1, zlib via `pako`.
`packfile`	Packfile reader and writer. ofs-delta, ref-delta, idx generation.
`protocol`	Smart-HTTP wire protocol — pkt-line framing, capabilities, refs advertisement, upload-pack / receive-pack negotiation.
`client`	High-level smart-HTTP client: `clone`, `fetch`, `push`.
`diff`	Myers line diff + tree diff.
`merge`	Three-way merge with conflict markers.
`refs`	Ref parsing, packed-refs, symbolic refs.

Quickstart — build a commit in memory

import {
  encodeBlob,
  encodeTree,
  encodeCommit,
  sha1,
  buildPackfile,
} from '@rehearse/git-core';

const blob = encodeBlob(new TextEncoder().encode('hello world\n'));
const blobSha = await sha1(blob);

const tree = encodeTree([
  { mode: '100644', name: 'README.md', sha: blobSha },
]);
const treeSha = await sha1(tree);

const commit = encodeCommit({
  treeSha,
  parents: [],
  author:    { name: 'Alice', email: 'a@example.com', timestamp: 1714500000, tzOffset: '+0000' },
  committer: { name: 'Alice', email: 'a@example.com', timestamp: 1714500000, tzOffset: '+0000' },
  message: 'init',
});
const commitSha = await sha1(commit);

// Pack the three objects together for transport
const pack = await buildPackfile([
  { sha: blobSha,   type: 'blob',   data: blob },
  { sha: treeSha,   type: 'tree',   data: tree },
  { sha: commitSha, type: 'commit', data: commit },
]);

Quickstart — clone a remote in pure TS

import { gitClone } from '@rehearse/git-core';

const result = await gitClone({
  url: 'https://github.com/honojs/hono.git',
  ref: 'refs/heads/main',
  // pluggable storage interface — write objects/refs to memory, fs,
  // R2, KV, whatever you have.
  storage: myObjectStore,
});

console.log(result.headSha);

Why pure TypeScript

Workers-friendly. No native deps, no child_process, no filesystem assumptions. Runs in any V8 isolate, including Cloudflare Workers and Durable Objects.
Auditable. ~2.4k lines of source, ~2.7k lines of tests. You can read the implementation in an afternoon.
Embeddable. Use it inside a CI tool, a code review bot, a VCS plugin, an MCP server — anywhere the git daemon would be too heavy.
Strongly typed. Every public surface has hand-written TypeScript types, not generated .d.ts retrofits.

Repo

Source, issues, roadmap: https://github.com/plsft/rehearse.

License

Apache 2.0.