When Nextcloud performs an upgrade or clean installation,
it will check whether /var/www/html/{config,data,custom_apps,themes} exist.
If not, it will copy
/usr/src/nextcloud/{config,data,custom_apps,themes} to /var/www/html.
This leads to a problem: If those subdirectories are existent but
empty, it will not do the copy. This situation is common when you mount
volumes to those subdirectories, like:
```
version: "2.1"
services:
app:
image: nextcloud:12-apache
volumes:
- nextcloud:/var/www/html:Z
- nextcloud-custom_apps:/var/www/html/custom_apps:Z
- nextcloud-config:/var/www/html/config:Z
- nextcloud-data:/var/www/html/data:Z
- nextcloud-themes:/var/www/html/themes:Z
ports:
- 8080:80/tcp
db:
image: mariadb
volumes:
- db:/var/lib/mysql:Z
environment:
MYSQL_USER: nextcloud
MYSQL_DATABASE: nextcloud
MYSQL_PASSWORD: nextcloud
MYSQL_ROOT_PASSWORD: nextcloud
volumes:
nextcloud:
nextcloud-custom_apps:
nextcloud-config:
nextcloud-data:
nextcloud-themes:
db:
```
This patch will fix this issue by copying to those subdirectories when they
are empty.
