Add more set options.

Author: YtvwlD

bin/backup

@@ -1,5 +1,7 @@
 #!/bin/sh
-set -e
+set -e # Exit if a command exists with an error.
+set -o pipefail # If any command in a pipe exits with an error, treat the whole pipe as failed.
+set -u # Fail if a variable is used, but not defined.
 [ -z "${BACKUP_NAME}" ] && { echo "error: BACKUP_NAME not set"; exit 1; }
 [ -z "${BACKUP_GPG_KEY_ID}" ] && { echo "error: BACKUP_GPG_KEY_ID not set"; exit 1; }
 [ -z "${BACKUP_SSH_DESTINATION}" ] && { echo "error: BACKUP_SSH_DESTINATION not set"; exit 1; }