Implement self-update recovery (T-403)

app-modern/cmd/softbox/main.go

@@ -19,6 +19,12 @@ import (
 const applicationEventCapacity = 32
 
 func main() {
+	if handled, err := acknowledgeInternalUpdateHealth(os.Args[1:]); handled {
+		if err != nil {
+			log.Printf("%s internal update health failed: %v", core.ProductName, err)
+			os.Exit(1)
+		}
+	}
 	go func() {
 		if err := run(); err != nil {
 			log.Printf("%s stopped: %v", core.ProductName, err)

app-modern/cmd/softbox/update_health.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"softbox.local/app-modern/platform/windows"
+	"softbox.local/core/updater"
+)
+
+func acknowledgeInternalUpdateHealth(arguments []string) (bool, error) {
+	if len(arguments) == 0 || arguments[0] != updater.InternalHealthFlag {
+		return false, nil
+	}
+	if len(arguments) != 2 {
+		return true, fmt.Errorf("%s requires exactly one internal request ID", updater.InternalHealthFlag)
+	}
+	executable, err := os.Executable()
+	if err != nil {
+		return true, fmt.Errorf("locate current executable: %w", err)
+	}
+	if err := updater.AcknowledgeHealthFromExecutable(executable, arguments[1], windows.New()); err != nil {
+		return true, fmt.Errorf("acknowledge self-update health: %w", err)
+	}
+	return true, nil
+}