diun: cleaner subject and watch local-build base images

docker/diun/diun.yml

@@ -8,6 +8,11 @@ providers:
   docker:
     watchByDefault: true      # watch every running container without needing labels
     watchStopped: false
+  file:
+    # Explicit watches for base images of locally-built containers (apps with a
+    # Dockerfile in their compose dir). The docker provider can't see these
+    # because the built image has a local-only tag with no registry digest.
+    filename: /diun.list.yml
 
 notif:
   mail:
@@ -19,4 +24,13 @@ notif:
     from: argento@fastmail.com
     to:
       - timothykim@fastmail.fm
+    # Subject leads with container name so the compose dir is obvious from the inbox
+    # (e.g. "nextcloud-redis" -> docker/nextcloud/). Default template uses the full
+    # canonical ref with @sha256 digest, which is unreadable.
+    templateTitle: '[{{ .Entry.Status }}] {{ .Entry.Metadata.ctn_names }} ({{ .Entry.Image.Path }}:{{ .Entry.Image.Tag }})'
+    templateBody: |
+      Container: {{ .Entry.Metadata.ctn_names }}
+      Image:     {{ .Entry.Image.Path }}:{{ .Entry.Image.Tag }}
+      {{ if .Entry.Image.HubLink }}Link:      {{ .Entry.Image.HubLink }}{{ end }}
+      Host:      {{ .Meta.Hostname }}