cmd/mbf: optionally export output

This is for debugging for now, as no program consumes this format yet.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/mbf/main.go

@@ -435,6 +435,7 @@ func main() {
 	{
 		var (
 			flagDump   string
+			flagExport string
 		)
 		c.NewCommand(
 			"cure",
@@ -447,10 +448,34 @@ func main() {
 					return fmt.Errorf("unknown artifact %q", args[0])
 				} else if flagDump == "" {
 					pathname, _, err := cache.Cure(rosa.Std.Load(p))
-					if err == nil {
-						log.Println(pathname)
-					}
+					if err != nil {
 						return err
+					}
+					log.Println(pathname)
+
+					if flagExport != "" {
+						msg.Verbosef("exporting %s to %s...", args[0], flagExport)
+
+						var f *os.File
+						if f, err = os.OpenFile(
+							flagExport,
+							os.O_WRONLY|os.O_CREATE|os.O_EXCL,
+							0400,
+						); err != nil {
+							return err
+						} else if _, err = pkg.Flatten(
+							os.DirFS(pathname.String()),
+							".",
+							f,
+						); err != nil {
+							_ = f.Close()
+							return err
+						} else if err = f.Close(); err != nil {
+							return err
+						}
+					}
+
+					return nil
 				} else {
 					f, err := os.OpenFile(
 						flagDump,
@@ -474,6 +499,11 @@ func main() {
 				&flagDump,
 				"dump", command.StringFlag(""),
 				"Write IR to specified pathname and terminate",
+			).
+			Flag(
+				&flagExport,
+				"export", command.StringFlag(""),
+				"Export cured artifact to specified pathname",
 			)
 	}