chisel-wrapper

#!/bin/bash

set -eu

CHISEL_BIN="${CHISEL_BIN:-"chisel"}"

CHISEL_CACHE_DIR="$(mktemp -d)"
CHISEL_DPKG_STATUS_FILE=""

print_usage() {
	cat <<- EOF
	Usage: $(basename "$0") [OPTIONS] -- [chisel-cut-OPTIONS] <slice names..>

	This wrapper script performs "chisel cut" operation on specified slices.
	And if specified in OPTIONS, it performs various tasks such as generating
	a dpkg status file for the installed file system.

	Every argument after -- will be passed to "chisel cut".

	[OPTIONS]

	  --generate-dpkg-status <path>
	      Generate a dpkg status file at the specified <path>.

	  -h, --help
	      Print this help information and quit.

	ENVIRONMENT VARIABLES

	  CHISEL_BIN
	      Set CHISEL_BIN to the location of the chisel binary.
	      By default, it will look for "chisel" in PATH.
	EOF
}

cleanup() {
	if [ -d "$CHISEL_CACHE_DIR" ]; then
		rm -rf "$CHISEL_CACHE_DIR"
	fi
}
trap cleanup EXIT

print_error() {
	echo "Error:" "$@" >&2
}

install_slices() {
	XDG_CACHE_HOME="$CHISEL_CACHE_DIR" $CHISEL_BIN cut "$@"
}

prepare_dpkg_status() {
	dir="$CHISEL_CACHE_DIR/chisel/sha256"
	if [ ! -d "$dir" ]; then
		print_error "could not find the chisel cache at ${dir}"
		exit 1
	fi

	if [ -f "$CHISEL_DPKG_STATUS_FILE" ]; then
		rm -f "$CHISEL_DPKG_STATUS_FILE"
	fi

	for f in "$dir"/*; do
		is_deb="$(file "$f" | grep "Debian binary package" | cat)"
		if [ -z "$is_deb" ]; then
			continue
		fi
		dpkg-deb -f "$f" >> "$CHISEL_DPKG_STATUS_FILE"
		echo "" >> "$CHISEL_DPKG_STATUS_FILE"
	done
}

while (( "$#" )); do
	case "$1" in
		--generate-dpkg-status)
			if (( "$#" < 2 )); then
				print_error "Please specify the desired path of the dpkg status file."
				exit 1
			fi
			CHISEL_DPKG_STATUS_FILE="$2"
			shift 2
			;;
		-h|--help)
			print_usage
			exit 0
			;;
		--)
			shift
			break
			;;
		-*)
			echo "Unknown option: $1"
			exit 1
			;;
		*)
			echo "Unexpected argument: $1"
			exit 1
			;;
	esac
done

install_slices "$@"

if [ -n "$CHISEL_DPKG_STATUS_FILE" ]; then
	prepare_dpkg_status
fi