Have a "xml changed on disk. Do you want to reload the file" warning in diamond if a file changes while its open in diamond.

It would be great to have a "File changed" warning similar to what gedit has.
I imagine it to work as follows:
1) Open a flml file in diamond (and keep it running)
2) Open that flml file in an editor and change its content
3) When going back to the diamond window, a "file changed" warning should come up asking if the user wants to reload the file,