bug#66903: 29.1; shell-mode directory tracking incorrectly handles double slashes

[Eshel Yaron via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Hi,

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Allen Li <darkfeline@felesatra.moe>
>> Date: Fri, 3 Nov 2023 00:22:26 -0700
>> Cc: 66903@debbugs.gnu.org
>>
>> On Fri, Nov 3, 2023 at 12:16 AM Eli Zaretskii <eliz@gnu.org> wrote:
>>
>>  "M-x shell" is not a shell, it is an Emacs interface to a shell.
>>  Thus, it should be free to implement behavior not present in the
>>  shell, if we consider it convenient for Emacs users.
>>
>> The behavior it is supposed to implement is that it tracks the working directory of the shell.
>> Currently, it fails to do so for most shells that a user would use.
>> In fact, it fails to do so for the default value `/bin/bash`.
>>
>>  > It looks like this should be fixed in `shell-cd` (which should also fix
>>  > `shell-process-pushd`) by implementing "custom" path handling (compared
>>  > to Emacs default path handling behavior).
>>
>>  This is not a bug.  I'm okay with adding a new optional feature that
>>  would disable the above behavior, but it must be off by default.
>>
>> This is absolutely a bug.  The feature, where shell-mode attempts to track the working
>> directory of its subshell, fails to work for most shells in existence
>> (e.g., derivatives of POSIX sh, csh, zsh, etc.) and including the default shell.
>>
>> I agree it may be an option, but I disagree that it should be off by default, given that the
>> default configured shell Bash requires it.
>
> I think we disagree about what should be fixed: the value of
> default-directory or the directory to which "cd ~//bin" switches.

IIUC what you're implying here is that "cd ~//bin" should actually
switch the shell's current directory to /bin instead of ~/bin, is that
right?

I just wanted to note that this is not really an option with M-x shell,
because it is the shell, and not Emacs, that interprets "cd" and changes
directory.  Emacs just tracks certain shell commands and tries to keep
the buffer's `default-directory` up to date with the shell's directory.


Best,

Eshel