add hadolint

.drone.yml

@@ -5,6 +5,9 @@ name: default
 
 steps:
 
+- name: validate
+    image: bunix42/pre-commit
+
 - name: nextcloud-22-fpm
   image: plugins/docker
   settings:

.gitignore

@@ -0,0 +1 @@
+pre-commit-cache

.pre-commit-config.yaml

@@ -0,0 +1,6 @@
+repos:
+  - repo: https://github.com/hadolint/hadolint
+    rev: master
+    hooks:
+      - id: hadolint
+        args: [--ignore, DL3008]

Dockerfile

@@ -3,6 +3,6 @@ FROM nextcloud:${NEXTCLOUD_VERSION}
 
 LABEL org.opencontainers.image.authors="hanjo@bunix.de"
 
-RUN apt-get update && apt-get install -y \
-        python3 \
+RUN apt-get update \
+    && apt-get install --no-install-recommends -y python3 \
     && rm -rf /var/lib/apt/lists/*