Persist nix channel state

nix.attrs

@@ -1,4 +1,3 @@
-# cat nix | grep -v '^#' | while read -r drv; do nix-env -q "${drv%%_*}" || nix-env -iA nixpkgs."${drv}"; done
 bat
 borgbackup
 ccache

nix.channel

@@ -0,0 +1 @@
+https://github.com/NixOS/nixpkgs/archive/14d9b465c71.tar.gz

nix.sh

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+
+set -e
+set -u
+set -o pipefail
+
+function setup() {
+    if grep -e 'experimental-features' /etc/nix/nix.conf; then
+        :
+    else
+        echo 'experimental-features = nix-command flakes' | sudo tee -a /etc/nix/nix.conf
+    fi
+}
+
+function save() {
+    commit=$(nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version' | perl -n -e '/".*\.([a-z0-9]+)"/ and print "$1\n"')
+    channel="https://github.com/NixOS/nixpkgs/archive/${commit}.tar.gz"
+    echo "saving: ${channel}"
+    echo "${channel}" > nix.channel
+}
+
+function install() {
+    channel="$(cat nix.channel)"
+    echo "using: ${channel}"
+
+    declare -a attrs=()
+    while IFS='' read -r line || [[ -n "${line}" ]]; do
+        attrs+=("${line}")
+    done < nix.attrs
+
+    declare -a args=()
+    for attr in "${attrs[@]}"; do
+        args+=("-A" "${attr}")
+    done
+
+    nix-env -f "${channel}" -i "${args[@]}"
+}
+
+function update() {
+    nix-channel --update
+    save
+    install
+}
+
+function usage() {
+    echo 'usage: nix.sh [setup|save|install|update]' 1>&2
+    exit 1
+}
+
+case "${1:-}" in
+    setup)
+        setup
+        ;;
+    save)
+        save
+        ;;
+    install)
+        install
+        ;;
+    update)
+        update
+        ;;
+    upgrade)
+        upgrade
+        ;;
+    *)
+        usage
+        ;;
+esac