[dev.go2go] cmd/go2go: add -brackets option

Change-Id: I5c3d36df3d84ad85d2fb70152f5692223cf6cfb6
Reviewed-on: https://go-review.googlesource.com/c/go/+/243161
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/go2go/doc.go

@@ -7,7 +7,13 @@
 //
 // Usage:
 //
-//	go2go <command> [arguments]
+//	go2go [options] <command> [arguments]
+//
+// The only option is -brackets, which requires square brackets rather
+// than parentheses for generic code. This is temporarily useful when
+// translating code that uses square brackets to pass type arguments
+// to generic function and types while not defining any generic
+// functions or types itself.
 //
 // The commands are:
 //

src/cmd/go2go/main.go

@@ -26,6 +26,12 @@ var cmds = map[string]bool{
 	"translate": true,
 }
 
+var useBrackets bool
+
+func init() {
+	flag.BoolVar(&useBrackets, "brackets", false, "expect square brackets for generics")
+}
+
 func main() {
 	flag.Usage = usage
 	flag.Parse()
@@ -46,6 +52,9 @@ func main() {
 	defer os.RemoveAll(importerTmpdir)
 
 	importer := go2go.NewImporter(importerTmpdir)
+	if useBrackets {
+		importer.UseBrackets = true
+	}
 
 	var rundir string
 	if args[0] == "run" {