Pre push hook to prevent push of commits less than 30 mins old

pre-push

#!/bin/bash                                                                                                             

commit_timestamp=$(date -d @$(git log -n1 --format="%at") +%Y%m%d%H%M)
now=$(date +%s)
difference=($now - $commit_timestamp)
max=$((30 * 60))
if [ "$difference" -lt "$max" ]
then
    echo "Too soon"
    exit 1
fi
exit 0