Sorry to revive an old topic if it’s not relevant anymore… I use the post-receive hook method @BenSeitz described and it’s very fast and reliable in my experience. As @dinko pointed out, doing that makes you deploy on the production server git-related stuff which some people might not want to do since it uses disk space unnecessarily on the production server, and as you also pointed out, it doesn’t sync the other way around to reflect content changes on the production server to a remote repo (that just happens to not be a problem for me since there is no direct modification of content on the production server in my workflow – this however seems to be discussed here), but what i’m wondering about is if i really need to also have a post-receive hook (as i do) for each of the core, toolkit and panel repos. When i update the infrastructure, i have to push 3 git repos to the production server via those hooks. Is there a better way? It’s not an issue for me since i’m just doing that a couple times a year, and on one server. I’m just curious to understand if i’m doing something stupid 
EDIT: i just found this thread in the forum which seems to say that pushing just once taking submodules into account is not totally straighforward if you want to separate the repos from the work tree on the production server… I also second @Mattrushka’s idea that a ‘small & simple deployment guide for Kirby’ would probably be helpful.