feat(master): suggest newer version tags for third-party images (#11) (#31)

internal/master/model/model.go

@@ -66,6 +66,11 @@ type Service struct {
 	AvailableSource string // SourceWebhook or SourcePoll; "" when AvailableRef is empty
 	AvailableAt     *time.Time
 	LastPollError   string // last registry error for the followed ref; "" when fine
+	// NewerRef is the newest repo:tag from the registry's tag list that
+	// tagver.Newer finds for the followed tag; "" if none. A suggestion only:
+	// it is never deployed automatically, not even for auto services.
+	NewerRef string
+	NewerAt  *time.Time // when NewerRef was first suggested; nil when NewerRef is empty
 	// LastTagDigest is the newest digest of the followed tag that was deployed
 	// or started: set when the poller starts an auto job, when it sees the service
 	// already running that digest, and when any plain tag job succeeds (the
@@ -95,6 +100,9 @@ const (
 	// SourceRunning is used by image_versions only: an agent reported the
 	// version as running.
 	SourceRunning = "running"
+	// SourceTags is used by image_versions only: the tag appeared in the
+	// registry's tag list as a newer tag.
+	SourceTags = "tags"
 )
 
 // Available is a newer ref reported for a service.
@@ -113,7 +121,7 @@ type ImageVersion struct {
 	Repo        string
 	Tag         string
 	Digest      string
-	Source      string // SourceWebhook, SourcePoll or SourceRunning: the first source that saw it
+	Source      string // SourceWebhook, SourcePoll, SourceRunning or SourceTags: the first source that saw it
 	FirstSeenAt time.Time
 }