(defun ask-user-about-lock (file opponent)
"Ask user what to do when he wants to edit FILE but it is locked by OPPONENT.
This function has a choice of three things to do:
- do (signal 'buffer-file-locked (list FILE OPPONENT))
+ do (signal 'file-locked (list FILE OPPONENT))
to refrain from editing the file
return t (grab the lock on the file)
return nil (edit the file even though it is locked).