edits = append(edits, func(f *modfile.File) {
		if err := f.DropGodebug(arg); err != nil {
			base.Fatalf("go: -dropgodebug=%s: %v", arg, err)
		}
	})
}

// flagRequire implements the -require flag.
func flagRequire(arg string) {
	path, version := parsePathVersion("require", arg)
	edits = append(edits, func(f *modfile.File) {
		if err := f.AddRequire(path, version); err != nil {