Remote git pull to update multiple servers

/home/web/server_hosts

server1
server2
server3

/home/web/server_update.sh
#!/bin/bash

for host in `cat /home/web/server_hosts`
do
ssh -t $host 'cd /opt/www/; git pull'
echo $host " has been updated"
done

Make sure the current user of the script has the permissions to ssh remote servers and do `git pull ` on the server.