dev-setup-from-21.05

#!/usr/bin/env bash
# Usage: eval `./dev-setup2`
set -e

# ensure PWD is the directory this script resides in (allows calls like ../dev-setup or $HOME/fc-nixos/dev-setup)
cd "$(dirname "$(readlink -f "$0")")"

base=$PWD
# preserve nixos-config
config=$(nix-instantiate --find-file nixos-config 2>/dev/null) || true

# bootstrapping with what we find on the system
if [[ ! -e /tmp/nixos-2411-bootstrap/nixpkgs ]]; then
    rm -rf /tmp/nixos-2411-bootstrap
    mkdir /tmp/nixos-2411-bootstrap
    cd /tmp/nixos-2411-bootstrap
    curl -o nixpkgs.tar.gz -L https://github.com/flyingcircusio/nixpkgs/archive/refs/heads/nixos-24.11.tar.gz
    tar xf nixpkgs.tar.gz
    ln -s nixpkgs-nixos-24.11 nixpkgs
fi
cd $base
NIX_PATH="/tmp/nixos-2411-bootstrap"
export NIX_PATH
channels=`nix-build -Q --quiet versions.nix -A allUpstreams --no-out-link`
if [[ -z $channels ]]; then
    echo "$0: failed to build nixpkgs+overlay" >&2
    exit 1
fi
mkdir -p channels
find $channels -maxdepth 1 -type l | while read channel; do
    target="channels/${channel##*/}"
    # don't toucn anything which is not a link into the nix store
    if [[ ! -L $target && -d $target ]]; then
        echo "$0: warning: $target appears to be a local dev checkout" >&2
        continue
    elif [[ -L $target && $(readlink $target) != /nix/store/* ]]; then
        echo "$0: warning: $target appears to be a local dev checkout" >&2
        continue
    fi
    ln -fs $channel channels
done
if ! [[ -e channels/fc ]]; then
    ln -s .. channels/fc
fi

NIX_PATH="$base/channels"
if [[ -n "$config" ]]; then
    NIX_PATH="${NIX_PATH}:nixos-config=$config"
else
    NIX_PATH="${NIX_PATH}:nixos-config=${base}/nixos"
fi

echo "export NIX_PATH=$NIX_PATH"