CI: Only update image on new releases

.drone.yml

@@ -24,6 +24,23 @@ steps:
     depends_on:
       - submodules
 
+  - name: Check for new posts
+    image: klakegg/hugo:alpine
+    pull: always
+    commands:
+      # If this is a cronjob and there are no new pages to publish fail successfully (exit status 78)
+      - export TIMESTAMP_YESTERDAY=$(date -d @$(($(date +%s) - 86400)) -u +"%Y-%m-%dT%H:%M:%SZ")
+      - export POST_YESTERDAY=$(hugo list future --clock $TIMESTAMP_YESTERDAY | md5sum)
+      - export POST_TODAY=$(hugo list future | md5sum)
+      - if [ "$POST_YESTERDAY" = "$POST_TODAY" ]; then exit 78; fi
+      - exit 0
+    depends_on:
+      - Compress Images
+      - submodules
+    when:
+      event:
+        - cron
+
   - name: Build HTML
     image: klakegg/hugo:alpine
     commands:
@@ -31,6 +48,7 @@ steps:
     depends_on:
       - Compress Images
       - submodules
+      - Check for new posts
 
   - name: Build Image
     image: plugins/docker