To update the already installed templates, use the following request:
XML Request Example
curl -i -X PUT -u 'user:userpass' http://test/templates/12/upgrade.xml -H 'Accept: application/xml' -H 'Content-type: application/xml'
JSON Request Example
curl -i -X PUT -u 'user:userpass' http://test/templates/12/upgrade.json -H 'Accept: application/json' -H 'Content-type: application/json'
id - the ID of the required template