bug#66338: 30.0.50; grep-commnd set and using an old fish results in empty Copyright files

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

Eli Zaretskii <eliz@gnu.org> writes:

> The Emacs manual says:
>
>   ‘SHELL’
>        The name of an interpreter used to parse and execute programs run
>        from inside Emacs.  This is used to initialize the variable
>        ‘shell-file-name’ (*note Single Shell::).
>
> So Emacs expects this variable to point to a shell that Emacs can use
> to run programs, not your interactive shell.  If you want a different
> shell to be used in interactive shell sessions, such as "M-x shell",
> then you should use the variable explicit-shell-file-name to point to
> that other shell (in your case, fish).

I understand that this is what Emacs expects. It seems to me that other
parts of a user’s system might go against this expectation, however. The
man page for login(1) says this, for example:

       Your user and group ID will be set according to their values in
       the /etc/passwd file. The value for $HOME, $SHELL, $PATH,
       $LOGNAME, and $MAIL are set according to the appropriate fields
       in the password entry. Ulimit, umask and nice values may also be
       set according to entries in the GECOS field.

That is to say, if a users runs chsh(1) and decides to use fish, then
SHELL is set to fish, it is inherited to all processes, and Emacs
breaks.

The Emacs manual also says the following in (elisp) Security
Considerations, which is consistent with what you said above (and
unfortunate for users like me):

     Emacs has customization and other variables with similar
     considerations.  For example, if the variable ‘shell-file-name’
     specifies a shell with nonstandard behavior, an Emacs-based
     application may misbehave.

Too bad that there is not even a warning.

I’ll try to close this bug.