improve logging

store/tag.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	log "github.com/sirupsen/logrus"
 	"os"
+	"strings"
 	"time"
 )
 
@@ -149,7 +150,7 @@ func (s *Store) TagType(tag, t string) {
 	}
 
 	if !TagTypeAllowed(t) {
-		log.Warnf("Invalid tag change on tag %s, got %s, expecting %s", tag, t, AllowedTagTypes)
+		log.Warnf("Invalid tag change on tag %s, got %s, expecting one of %s.", tag, t, strings.Join(AllowedTagTypes, ", "))
 		return
 	}
 	info := s.TagInfo(tag)