RE: diff-mode

[Drew Adams]

> Anyway the error I get when in my configuration I try to kill 
> the ediff session is
> 
> --8<---------------cut here---------------start------------->8---
> Quit this Ediff session & show containing session group? (y or n) 
> ediff-cleanup-mess: Attempt to delete minibuffer or sole 
> ordinary window
> --8<---------------cut here---------------end--------------->8---

Great.  Now you can report a bug: `M-x report-emacs-bug'.  

First: Load library `ediff-util.el' (the library where `ediff-cleanup-mess' is
defined.  Be sure to include the ".el" here, so you don't just load the
byte-compiled file.

Second: `M-x set-variable RET debug-on-error RET t RET', to show a backtrace
when the error is raised.  Include the backtrace in your bug report.


_If_ you want to dig further to help find the problem, you can try to follow
function `ediff-cleanup-mess' in the debugger:

M-x debug-on-entry RET ediff-cleanup-mess RET

When you try to quit `ediff', the debugger will open when `ediff-cleanup-mess'
is invoked.  Use `d' to step through the debugger (or `c' to skip through a
step).  You can add any info you learn this way to your bug report.  (You can
use command `cancel-debug-on-entry' to cancel `debug-on-entry'.)

Essentially, the problem here is that there is only one window in the Ediff
control frame, and Emacs tries to delete that lone window, which is a no-no.
What Emacs should be doing here (probably) is to delete the frame.  Instead, it
thinks you want to keep the frame and it complains that it cannot delete the
last window in the frame.  IMO, this is a bug.