bug#19865: tar-untar-buffer: should honor default-directory

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Cc: ivan@siamics.net, 19865@debbugs.gnu.org
> Date: Sun, 15 Feb 2015 20:43:17 -0500
> 
> I don't see why you object

I can only re-iterate what I already said: we shouldn't cater to
marginal use cases like that with code that is "tricky" (a.k.a.
"maintenance headache").  People who change directories of their
buffers should (and do) know what they are doing.  If doing that
causes them annoyances, they will know better next time.

> the command is executed by the user in one
> buffer, and it just so happens that its implementation switches
> to some internal auxiliary buffer.  The value of `default-directory'
> that should be used is the one that the user knows about, not the one
> kept by the hidden buffer, over which the user has no control.

Are we still talking about the situation where a user did "M-x cd"?
Or is this another use case?  If the latter, please describe it in its
entirety.  If the former, then is there still a problem if the user
refrains from "M-x cd"?

> This behavior is an unintended result of my change in tar-mode where we
> now have 2 buffers (rather than keeping all the raw tar data in the same
> buffer as the pretty list, hidden via narrowing).

Understood, but unintended results do not necessarily need fixes, just
because they are unintended.  The important question is: what, if any,
real problems are caused as unintended results?  We are discussing
those problems, so the fact that they are unintended results doesn't
seem important to me.