Ship the customizations as a Docker image

The Docker image is used in the initialization process, to copy
everything in the custom folder to the Gitea data dir (mounted as a
persistent volume). It is built using Packer and is based on the busybox
image, so we can use its minimalist shell system to copy files and set
permissions

README.md

@@ -3,10 +3,22 @@
 This repository contains configuration files and other assets, that are used to
 deploy and operate this Gitea instance.
 
-To upload the customization files to the running pod:
+To create a new image containing the customizations:
+
+Edit `packer/custom.json` to increment the tag, then run this script (needs
+[Packer](https://www.packer.io/) in your path)
 
 ```
-./script/copy_customization
+./script/build_customizations_image
+```
+
+Then edit `kubernetes/gitea-server.yaml` to use the new tag
+(`image: eu.gcr.io/fluted-magpie-218106/gitea_custom:$VERSION`) and apply the
+change:
+
+```
+cd kubernetes
+kubectl apply -f gitea-server.yaml
 ```
 
 Feel free to [open issues] for questions, suggestions, bugs, to-do items, and