bug#1226: Desktop holds second Emacs session hostage; C-x C-c doesn't work properly.

[Alan Mackenzie]

(i) With desktop enabled, start emacs.

(ii) Start a second emacs session.

Emacs2 detects Emacs1 and the danger of contention over .emacs.desktop.
It prompts thusly:

    "Warning: desktop file appears to be in use by PID 3616.
     Using it may cause conflicts.  Use it anyway? (y or n)"

(iii) Type n.

(iv) Attempt C-c C-x.

Emacs2 decides, because desktop is "enabled", that it wants to save a
desktop file, and prompts:

    "Directory for desktop file: ~/"

At this point, C-g aborts the "end Emacs" command.  One now has the
unpleasant choice of killing Emacs2 from the (operating system) console
or typing in some random directory to dump the empty .emacs.desktop to.

This is a bug.

Even worse, accepting the prompt's default directory, ~/, might
overwrite the real .emacs.desktop.

-- 
Alan Mackenzie (Nuremberg, Germany).