add unpack script to every snapshot

unpack.sh

@@ -0,0 +1,24 @@
+#! /bin/zsh
+
+TIMESTAMP=($(basename "$(pwd)"))
+OUTDIR="$1"
+KEYFILE="$2"
+
+function die {
+	>&2 echo "$2"
+	exit $1
+}
+
+[[ "$0" != "./unpack.sh" ]] && die 1 "This can only be executed from the snapshot directory itself."
+[[ ! -d "$OUTDIR" ]]       && die 1 "The first argument must be a directory to unpack subvolumes into."
+[[ ! -f "$KEYFILE" ]]      && die 1 "The second argument must be a readable keyfile."
+./check-integrity.sh       || die 2 "This snapshot failed integrity checks."
+
+### end of checks
+
+for ARCHIVE in *btrfs.zst.aes
+do
+	openssl enc -d -aes-256-cbc -pbkdf2 -salt -pass "file:$KEYFILE" < "$ARCHIVE" | zstd -d | btrfs receive "$OUTDIR" || die 3 "Failed to unpack subvolume."
+	SUBVOL_NAME=${ARCHIVE%%.btrfs.zst.aes}
+	mv "${OUTDIR}/${SUBVOL_NAME}" "${OUTDIR}/${SUBVOL_NAME}.${TIMESTAMP[1]}" || die 4 "Failed to rename subvolume."
+done