I have been given the task of deploying some changes made directly to the Seattle master page in the root site of our Intranet site collection.
My question is what is the correct way of applying this to all existing and new sub-sites and also across three site collections? I also need to make sure it doesn't change the my-sites / search pages as I believe they use difference master pages altogether.
I have done something similar with a public SharePoint portal but that was in SP 2010 and I was using Publishing Sites, which we are not in this case so I can't seem to just say inherit master-page from the parent.
Any pointer in the right direction would be great as I Want to make sure I'm doing this in the right way.