Open the same directory twice

On command line, I could open a directory like:

    code .

Now, I want two of the identical diretory opened and displayed in another window.
(It's not spliting the editor)
Then, I tried again.

    code .

Nothing happened.
There's still one directory opened.
How to achieve such a task?

You can do this with the following ways:

1- Manually open a new window (ctrlshiftn) and go to:

File > Add folder to Workspace. Then just select the folder.

2- Open the command panel (ctrlshiftp) enter dupl and hit enter that will duplicate the current workspace in a new window
*dupl is just a filter for the complete command that is: Workspaces: Duplicate Workspace in New Window thanks to dipnlink comment

Source: https://code.visualstudio.com/docs/editor/multi-root-workspaces
*Done in windows (10), vscode (1.35.1)

In the latest version, it is actually much simpler. In a window of the project you want to duplicate, open the command panel (Command + Shift + P in Mac or Ctrl + Shift + P in Ubuntu), then type dupl (and select Workspaces: Duplicate As Workspace in New Window), this will duplicate your workspace in a new window. Now you can have 2 windows of the same project at the same time.

Click Add workspace folder... and open the same folder. Works for me, other solution doesn't work, just jump focus to another window.