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.

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.

Successful responses are cached for 5 minutes.

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

The project is a simple script made with Deno. You can run it like this:

deno run --allow-net main.ts

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:

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

Make sure to trust the self-signed certificate Caddy generates. Then you should be able to run commands like this with no problem:

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