fix typo from test and add install.sh script

btrfs-snapshots.sh

@@ -6,7 +6,7 @@ TMP_MNT=${TMP_MNT:-/var/tmp/btrfs-backup}
 vols=()
 del=
 dryrun=0
-periodity=${a%/*}
+periodity=${0%/*}
 periodity=${periodity##*/}
 if [[ $periodity =~ ^cron\... ]]; then
     periodity=${periodity#cron}

install.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+for f in hourly daily weekly monthly; do
+    sudo cp btrfs-snapshots.sh /etc/cron.$f/btrfs-snapshots;
+done