endpoint for experimental installer

[abathur]

Hi @NixOS/marketing-team,

Not sure what we'll need to close the gap(s) here, but we hope to get releases of https://github.com/NixOS/experimental-nix-installer hosted under nixos.org. (Not replacing existing installer endpoints--it should clearly be an experiment.)

There's background in the infra issue we opened earlier this year:

• Host experimental-nix-installer binaries infra#452

Reaching out as the infra team suggested in issue above now that we have a release workflow set up.

The current tentative prerelease should be accessible via something like:

curl --proto '=https' --tlsv1.2 -sSf -L https://github.com/NixOS/experimental-nix-installer/releases/download/0.27.0/nix-installer.sh | sh -s -- --help

I'm not sure how ~controlled the sanctioning of a latest release should be, but I did also briefly un-toggle the prerelease status in order to confirm the latest release per github would also be accessible as:

curl --proto '=https' --tlsv1.2 -sSf -L https://github.com/NixOS/experimental-nix-installer/releases/latest/download/nix-installer.sh | sh -s -- --help

(I toggled it back to prerelease since we've already had people ~depend on this installer as we work, making me skittish about leaving a normal release sitting around for unknown amount of time without a clear go-ahead.)

cc @tomberek @roberth @mkenigs