Docker images are handy but it can get a a hassle to keep them updated. Also when a repository is automated you want to get these images when they get out.
One could setup a complex action/hook-based workflow using probes, but there is a nice, easy to use docker image that solves this issue and could prove useful: [watchtower](https://hub.docker.com/r/containrrr/watchtower).
When you are pulling new images in automaticly it is nice to have them cleaned as well. There is also a docker images for this (from Spotify). The image is: [spotify/docker-gc](https://hub.docker.com/r/spotify/docker-gc/).