It is possible that you require code to be in sync, for example if you are using load balancing technique and you have 2 of the same sites & repository installed. You do not want to come across a situation that 1 is behind with code.

Thats why we've added synchronized deployments, you can find this under the repository tab:

If you press this a modal will open with all the sites that contain a repository, so you can keep these in sync:

Select all the sites you need to be deployed once the main site is deployed and the rest will be done automatically for you.