git-patch-native

Rust-backed Node/Bun-oriented package for generating git-style unified patch strings from in-memory file changes.

import { generatePatch } from "git-patch-native";

const patch = generatePatch({
  "src/main.ts": {
    before: "const value = 1;\n",
    after: "const value = 2;\n",
  },
  "src/added.ts": {
    after: "export const added = true;\n",
  },
  "src/new-name.ts": {
    moved: "src/old-name.ts",
    before: "same\n",
    after: "same\n",
  },
});

API shape

generatePatch(changes, options?) accepts a record whose key is the new path, except deletions where the key is the deleted path.

type GitFileMode = "100644" | "100755";

type Changes = Record<string, {
  before?: string | null; // omitted for additions
  after?: string | null;  // omitted for deletions
  moved?: string | { from: string; similarity?: number };
  mode?: GitFileMode | { before?: GitFileMode | null; after?: GitFileMode | null };
}>;

Guarantees for the initial contract:

• deterministic path ordering
• git-style diff --git, ---, +++, hunk, add/delete, and rename headers
• path separator normalization to /
• Git-compatible C-style quoting for paths containing quotes or control characters
• new file mode, deleted file mode, old mode, and new mode headers for 100644/100755 mode metadata
• NUL paths and NUL content are rejected
• final-newline markers when needed
• contextLines >= 1 so output applies with default git apply
• text-only input: NUL-containing content is rejected
• all diff formatting owned by Rust core; JS only serializes inputs and loads the native binding

Development

npm install
npm run build
npm test
cargo test
npm run smoke:pack

The native package is currently local-build first. scripts/copy-native.mjs copies the Rust Node-API cdylib into bin/*.node and the Bun FFI cdylib into bin/*.{dylib,so,dll}, following the same platform-tag idea used by .references/fff-package/packages/fff-node/package.json.

npm run smoke:pack verifies publish shape by packing the package, installing the tarball into clean temporary consumers, then proving both:

• Node can import the package and load the Node-API addon.
• Bun can dlopen the packaged FFI library through bun:ffi.

The public SDK entrypoint remains generatePatch; the FFI surface is a low-level packaging/runtime artifact.

Publishing

This package uses a two-tier npm publish shape:

• git-patch-native publishes the JS/TypeScript SDK once.
• git-patch-native-<platform> packages publish native Node-API and Bun FFI artifacts from a GitHub Actions matrix.

Release tags are v<package.json version>, for example v0.1.0. The release workflow publishes with npm provenance:

git tag v0.1.0
git push origin v0.1.0

Before the first release, configure npm Trusted Publishing for the main package and each platform package. Use repository colelawrence/git-patch-native and workflow .github/workflows/release.yml.

After publishing, verify package signatures/provenance metadata with npm:

npm view [email protected] dist.integrity dist.signatures
mkdir /tmp/git-patch-native-verify && cd /tmp/git-patch-native-verify
npm init -y
npm install [email protected]
npm audit signatures

The npm package page should also show provenance for packages published by the release workflow.

Reference architecture

The fff repo is vendored as a submodule at .references/fff-package. The package skeleton mirrors its useful Node-package decisions:

• ESM package with dist/src/index.js + generated declarations
• explicit os / cpu support metadata
• platform detection helpers
• local dev binary lookup under bin
• future-compatible platform package names for prebuilt artifacts

This project intentionally uses N-API instead of ffi-rs for the first native binding because N-API is the cleaner shared seam for Node and Bun.