add renovate config

Dockerfile

@@ -6,8 +6,9 @@ LABEL maintainer="Robert Kaussow <mail@geeklabor.de>" \
     org.label-schema.vendor="Robert Kaussow" \
     org.label-schema.schema-version="1.0"
 
-ARG BUILD_VERSION=master
-ENV KANBOARD_VERSION="${BUILD_VERSION:-master}"
+ARG BUILD_VERSION
+# renovate: datasource=github-releases depName=kanboard/kanboard
+ENV KANBOARD_VERSION="${BUILD_VERSION:-v1.2.15}"
 
 ADD overlay/ /
 

renovate.json

@@ -1,3 +1,12 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": ["config:base"],
+  "regexManagers": [
+    {
+      "fileMatch": ["^Dockerfile$"],
+      "matchStrings": [
+        "datasource=(?<datasource>.*?) depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\sENV .*?_VERSION=\"\\${.*:-(?<currentValue>.*)}\"\\s"
+      ]
+    }
+  ]
 }