Flake SemVer Redirector

Parses semantic version ranges in URLs and redirects them to matched tags in a GitHub/Gitea/Forgejo repository.

When enumerating the repo's tags, any tags that don't conform to semantic versioning will be skipped. If no version is matched, a list of these tags is returned in the error.

The full semantic version syntax is supported, including complex specifiers, such as 1.2.7 || >=1.2.9 <2.0.0. However not all syntax is supported directly in URLs: some special characters must be URL-encoded. See the semver library documentation for a more detailed description of the supported syntax.

The special case latest causes all semantic version parsing to be skipped and just returns the latest tag, making it possible to get the latest tag of flakes that don't conform to semantic versioning.

Successful responses from Git forges cached for 5 minutes.

If an Authorization header is present, it will be passed through to the Git forge. Such requests are not subject to any caching.

It also supports fetching Nixpkgs channels from channels.nixos.org. In that case, the first component is parsed as the target "status" (one of stable or rolling), and the second component is parsed as the target "variant" (one of primary, darwin, or small). If omitted, they default to stable and primary respectively.

Such URLs will redirect to the nixexprs.tar.xz file, which is often smaller and faster to fetch than the repo archive from github:NixOS/nixpkgs URLs.

Examples

Using the public instance located at https://flake.andre4ik3.dev:

{
  inputs = {
    # Get the current stable Nixpkgs channel (nixos-*.*):
    nixpkgs.url = "https://nixpkgs.flake.andre4ik3.dev";
    # Get the current stable Nixpkgs channel for Darwin (nixpkgs-*.*):
    nixpkgs-darwin.url = "https://nixpkgs.flake.andre4ik3.dev/darwin";
    # Get the current stable Nixpkgs small channel (nixos-*.*-small):
    nixpkgs-small.url = "https://nixpkgs.flake.andre4ik3.dev/small";
    # Get the latest Nix version:
    nix.url = "https://github.flake.andre4ik3.dev/NixOS/nix/*";
    # Or pin to a specific version while allowing patch updates:
    nix-28.url = "https://github.flake.andre4ik3.dev/NixOS/nix/2.28";
    # Get the latest stable Ghostty version:
    ghostty.url = "https://github.flake.andre4ik3.dev/ghostty-org/ghostty/*";
    # Using ^ syntax requires URL-encoding it ("^" is "%5E" in URL encoded form):
    lanzaboote.url = "https://github.flake.andre4ik3.dev/nix-community/lanzaboote/%5E0.4.2";
    # Get the latest 1.x Copyparty:
    copyparty.url = "https://github.flake.andre4ik3.dev/9001/copyparty/1";
    # Get the latest 2.91 Lix version:
    lix.url = "https://gitea.flake.andre4ik3.dev/git.lix.systems/lix-project/lix/2.91";
  };

  outputs = { ... }: { };
}

Running

This project uses Bun as the package manager and test runner. After installing Bun, run bun i to install dependencies, bun run check to check TypeScript types and linter errors, and bun test to run tests.

However, Bun cannot be used as the runtime due to its lack of support for the Web Cache API. The easiest way to run the project locally is with Deno, like this:

# Start listening on localhost:8000
deno run start

However it won't be very useful, since determining the handler is done via the URL subdomain. You'll want to get a wildcard domain, or at least some subdomains that start with github. for GitHub and gitea. for Gitea/Forgejo. (Or you could change the script to determine the handler differently. It's pretty simple after all.)

For local experimentation you can use Caddy with a configuration like this:

http://*.flake.localhost {
    reverse_proxy http://127.0.0.1:8000
}

Make sure *.flake.localhost resolves to 127.0.0.1 or ::1. Then you should be able to run commands like this with no problem:

nix flake show "http://github.flake.localhost/NixOS/nix/2"