[PATCH] Make extdiff work at root directory

[Alexis S. L. Carvalho]

Thus spake Andrei Vermel:
> >Can you send a similar patch that also changes the snapshot_node
> >function in the same way and uses the same name (say, "root") in both?
> 
> Good point. Please find attached.

(replying to the list)

Pushed to crew-stable.

Thanks

Alexis