Initial import

Signed-off-by: Gergely Nagy <me@gergo.csillger.hu>

install/action.yml

@@ -0,0 +1,16 @@
+---
+name: install-nix
+author: Gergely Nagy
+description: "Install the Nix package manager on non-NixOS hosts"
+inputs:
+  install-url:
+    description: "URL to download the installer from"
+    required: true
+    default: "https://nixos.org/nix/install"
+runs:
+  using: "composite"
+  steps:
+    - shell: bash
+      run: $GITHUB_ACTION_PATH/bin/install-nix
+      env:
+        INPUT_INSTALL_URL: ${{ inputs.install-url }}

install/bin/install-nix

@@ -0,0 +1,41 @@
+#! /usr/bin/env bash
+set -euo pipefail
+
+if type -p nix &>/dev/null; then
+    echo "Nix is already installed."
+    exit
+fi
+
+workdir=$(mktemp -d)
+trap 'rm -rf "$workdir"' EXIT
+
+preconfigure_nix() {
+    cat >"${workdir}/nix.conf" <<EOF
+build-users-group =
+experimental-features = nix-command flakes
+max-jobs = auto
+show-trace = true
+trusted-users = root ${USER:-}
+EOF
+
+    install -d -m 0755 /nix
+    install -d -m 0755 /etc/nix
+    cp "${workdir}/nix.conf" /etc/nix/nix.conf
+}
+
+download_installer() {
+    curl -sS -o "$workdir/install" -v --fail -L "${INPUT_INSTALL_URL:-https://nixos.org/nix/install}"
+}
+
+install_nix() {
+    bash "$workdir/install" --no-daemon --no-channel-add --yes
+}
+
+post_install() {
+    echo "$HOME/.nix-profile/bin" >> "$GITHUB_PATH"
+}
+
+preconfigure_nix
+download_installer
+install_nix
+post_install