#!/usr/bin/env nix-shell
#! nix-shell -i bash -p curl jq nix
#
#   Updates nixpkgs.json to the latest or chosen nixpkgs revision
#
#   Usage: ./update-nix
#          ./update-nix $rev
#          ./update-nix $owner $rev
#
#   Arguments default to owner=nixos and rev=master and refer
#   to the github owner of a nixpkgs fork and a git revision.
#
set -exo pipefail

owner="nixos"

if [ ! -z "$2" ]; then
    owner="$1"
    rev="$2"
else
    rev="${1:-master}"
fi

resolved_rev=$(curl "https://api.github.com/repos/${owner}/nixpkgs/commits?sha=${rev}" | jq -r 'first.sha')
url="https://github.com/${owner}/nixpkgs/archive/${resolved_rev}.tar.gz"
digest=$(nix-prefetch-url --unpack "$url")
echo "{\"url\": \"${url}\", \"sha256\": \"${digest}\"}" | jq '.' > nix/nixpkgs.json