Help to use File cheatcodes to access a file in an external project.

[pacelliv]

I want to programatically read and write a file in an external project using the File cheatcodes.

Given the following tree:

├─── MyFoundryProject
│   └─── folder
│      └─── file_1
│          
│   
├─── ExternalProject
   └─── folder
      └─── file_2

What would be the paths for: a) fs_permissions in my foundry.toml and for b) the readFile cheatcode to access file_2 from file_1.

I've tried a few combinations and all I get is that I don't have the permission to access file2.