use master instead of HEAD

applications/plex.yaml

@@ -1,3 +1,4 @@
+---
 apiVersion: argoproj.io/v1alpha1
 kind: Application
 metadata:
@@ -8,14 +9,14 @@ spec:
   sources:
     - repoURL: http://gitea-http.gitea.svc.cluster.local:3000/admin/kube-plex.git
       path: charts/kube-plex
-      targetRevision: HEAD
+      targetRevision: master
       ref: charts
       helm:
         releaseName: plex
         valueFiles:
           - $values/helm-values/plex_values.yml
     - repoURL: http://gitea-http.gitea.svc.cluster.local:3000/admin/turingpi.git
-      targetRevision: HEAD
+      targetRevision: master
       ref: values
   destination:
     server: https://kubernetes.default.svc