bug#12911: 24.3.50; let users decide where (& perhaps whether) `emacs_backtrace.txt'files are written

[Drew Adams]

> > FWIW, I'd be annoyed if I were a w32 user and had to deal with
> > emacs_backtrace.txt files appearing in directories without my saying
> > so explicitly.
> 
> Windows binaries for official releases (as opposed to trunk snapshots)
> rarely crash. It's not as if the user is going to get backtraces all
> over his hard disk on every single run.

FWIW, that is not my experience, not with Emacs 24.

Official Emacs binaries 24.1 and 24.2 crash for me, seemingly randomly, sooner
or later, pretty much each time I use them - and I don't get to use them for
long.  If I had a recipe I would send it along.  I sent an emacs-backtrace.txt
file recently, which Eli said should be useful, but no news yet on whether it
helped fix some bug. ;-)

I agree, however, that a user is not going to be getting backtraces all over the
place.  That's some consolation, but not reason enough by itself to introduce
this regression, IMHO (just one opinion).

As Eli himself said - and was the first to point out AFAIK
(http://lists.gnu.org/archive/html/emacs-devel/2012-09/msg00501.html):

EZ> Based on my experience, I expect this "feature" to be hated,
EZ> by users and Emacs maintainers alike.

I think he's likely to be right in that guess.  And he points out several
reasons against introducing this feature (reasons I'm not qualified to judge).

Eli also said, there:
EZ> using the limited information it provides can be quite difficult

Whether the feature is worth the various drawbacks mentioned, I, for one, cannot
say.

But it sure would be good to find a way to put these backtrace files somewhere
other than a user folder.  That I will say.

FWIW, both Emacs maintainers have seemed to agree.  Yidong said this
(http://lists.gnu.org/archive/html/emacs-devel/2012-09/msg00870.html):

CY> Littering the filesystem with these backtrace files is
CY> kind of obnoxious.

Certainly, plopping them into user folders is.  User data is not for Emacs to
fiddle with uninvited, and that includes folders.