#! /usr/bin/env nix-shell
#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/42a1c966be226125b48c384171c44c651c236c22.tar.gz -i bash -p git gnugrep gnused findutils nixfmt-tree
# Avoid being affected by system and user git config.
export GIT_CONFIG_NOSYSTEM=1
export HOME=/var/empty
export XDG_CONFIG_HOME=/var/empty

nixfmt_args=()
files=()

for arg do
    case $arg in
        -h)
            echo "$0 [-c]"
            exit
            ;;
        --ci)
            nixfmt_args+=("$arg")
            ;;
        -*)
            echo "unrecognised flag: $arg" >&2
            exit 1
            ;;
        *)
            files+=("$arg")
            ;;
    esac
done

git_root=$(git rev-parse --show-toplevel)

git ls-files -z --cached --others --full-name -- "${files[@]}" |
    grep -z '\.nix$' |
    sed -z "s|^|$git_root/|" |
    xargs -0 treefmt --no-cache "${nixfmt_args[@]}"