Prepare server

1. Use SSH to get to webspace: ssh user@webspace.host
2. Navigate to correct directory: cd myapp/production
3. Create Git folder: mkdir .git
4. Navigate to the folder: cd .git
5. Init bare repository: git init --bare
6. Create file called "post-receive" in .git/hooks with this content:

#!/bin/sh

The production directory

TARGET="/kunden/homepages/xx/xxx/htdocs/myapp/production/app"

The Git repo

REPO="/kunden/homepages/xx/xxx/htdocs/myapp/production/.git"

Deploy the content to the directory

git --work-tree=$TARGET --git-dir=$REPO checkout -f

Update: It's important that your "post-receive" file has the permission to execute. In my case, I gave the file permission 705.

Prepare local development setup

1. Project folder has to be a Git repository. If it isn't already, run: git init
2. Add remote: git remote add deploy ssh://user@webspace.host/kunden/homepages/xx/xxx/htdocs/myapp/production/.git

Upload changes

1. Commit local changes.
2. Run this to upload them: git push deploy HEAD