allow kubectl cmd to process dirs recursively

reqs:
    - the kubectl cmd must support the -f | --filename flag
    - the kubectl cmd must support visiting a dir one level deep,
    or using more than one resource

pkg/kubectl/cmd/rollout/rollout_undo.go

@@ -37,8 +37,10 @@ type UndoOptions struct {
 	Typer      runtime.ObjectTyper
 	Info       *resource.Info
 	ToRevision int64
-	Out        io.Writer
-	Filenames  []string
+
+	Out       io.Writer
+	Filenames []string
+	Recursive bool
 }
 
 const (
@@ -67,6 +69,7 @@ func NewCmdRolloutUndo(f *cmdutil.Factory, out io.Writer) *cobra.Command {
 	cmd.Flags().Int64("to-revision", 0, "The revision to rollback to. Default to 0 (last revision).")
 	usage := "Filename, directory, or URL to a file identifying the resource to get from a server."
 	kubectl.AddJsonFilenameFlag(cmd, &options.Filenames, usage)
+	cmdutil.AddRecursiveFlag(cmd, &options.Recursive)
 	return cmd
 }
 
@@ -86,7 +89,7 @@ func (o *UndoOptions) CompleteUndo(f *cmdutil.Factory, cmd *cobra.Command, out i
 
 	infos, err := resource.NewBuilder(o.Mapper, o.Typer, resource.ClientMapperFunc(f.ClientForMapping), f.Decoder(true)).
 		NamespaceParam(cmdNamespace).DefaultNamespace().
-		FilenameParam(enforceNamespace, o.Filenames...).
+		FilenameParam(enforceNamespace, o.Recursive, o.Filenames...).
 		ResourceTypeOrNameArgs(true, args...).
 		Latest().
 		Flatten().