shell.el: directory tracking can't cope with subshells

[era eriksson <era@iki.fi>]

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Please write in English, because the Emacs maintainers do not have
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In GNU Emacs 20.7.2 (i386-debian-linux-gnu, X toolkit)
 of Fri Apr  5 2002 on cyberhq modified by Debian
configured using `configure  i386-debian-linux-gnu --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes --with-x=yes --with-x-toolkit=yes'

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:


If I start a subshell in shell mode, and change directories inside
that subshell, the directory tracking code in shell.el is unable to
catch up with the previous state when I exit from the subshell and
return to (the working directory of) the shell where I invoked the
subshell.

I do not have a ready fix for this, but I think it should be possible
to add (a) code to handle "([b?a|k)sh" sort of like pushd; (b) code to
handle "exit" (and maybe "suspend"?) kind of like a mix of popd and
"cd -"; and (c) some sort of mechanics to keep a stack of directory
stacks so that you can simulate the underlying directory stacks
structure in the shells.

As far as I can tell, the modifications should not be major, but I
haven't tried to implement this. Maybe I'll follow up with a patch
eventually.

For the time being, please note this for the record,

/* era */

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