gui, lib/config: Add notification about new release channels

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3945

lib/config/config.go

@@ -21,12 +21,13 @@ import (
 
 	"github.com/syncthing/syncthing/lib/protocol"
 	"github.com/syncthing/syncthing/lib/rand"
+	"github.com/syncthing/syncthing/lib/upgrade"
 	"github.com/syncthing/syncthing/lib/util"
 )
 
 const (
 	OldestHandledVersion = 10
-	CurrentVersion       = 17
+	CurrentVersion       = 18
 	MaxRescanIntervalS   = 365 * 24 * 60 * 60
 )
 
@@ -257,6 +258,9 @@ func (cfg *Configuration) clean() error {
 	if cfg.Version == 16 {
 		convertV16V17(cfg)
 	}
+	if cfg.Version == 17 {
+		convertV17V18(cfg)
+	}
 
 	// Build a list of available devices
 	existingDevices := make(map[protocol.DeviceID]bool)
@@ -310,6 +314,24 @@ func (cfg *Configuration) clean() error {
 	return nil
 }
 
+func convertV17V18(cfg *Configuration) {
+	// Do channel selection for existing users. Those who have auto upgrades
+	// and usage reporting on default to the candidate channel. Others get
+	// stable.
+	if cfg.Options.URAccepted > 0 && cfg.Options.AutoUpgradeIntervalH > 0 {
+		cfg.Options.UpgradeToPreReleases = true
+	}
+
+	// Show a notification to explain what's going on, except if upgrades
+	// are disabled by compilation or environment variable in which case
+	// it's not relevant.
+	if !upgrade.DisabledByCompilation && os.Getenv("STNOUPGRADE") == "" {
+		cfg.Options.UnackedNotificationIDs = append(cfg.Options.UnackedNotificationIDs, "channelNotification")
+	}
+
+	cfg.Version = 18
+}
+
 func convertV14V15(cfg *Configuration) {
 	// Undo v0.13.0 broken migration