The FileChangedShell event:
Fires:
radio_button_unchecked
When Neovim notices that the modification time of a file has changed since editing started.
radio_button_unchecked
When the file attributes of the file change
radio_button_unchecked
When the size of the file changes.
Notes:
radio_button_unchecked
Fires for each file that is changed after executing a shell command.