bug#54487: 29.0.50; connection-local value for `shell-file-name' not set in Dired buffers over Tramp

[Jim Porter <jporterbugs@gmail.com>]

On 3/21/2022 7:06 AM, Michael Albinus wrote:
> I'll wait until Jim confirms that this works in general, then I would
> apply a patch along this spec.

The patch you posted works for me. Setting `shell-file-name' to 
"/bin/sh" worked in my tests because it makes the function 
`w32-shell-dos-semantics' return nil, so this condition in 
`shell-quote-argument' isn't matched:

   ((and (eq system-type 'windows-nt) (w32-shell-dos-semantics))

That makes the shell-quoting use POSIX-style rules instead, which is 
what we want if the default-directory is remote. Reading that code, I 
think the `w32-shell-dos-semantics' part of that condition is there to 
handle things like Cygwin builds, so maybe it's not quite right to rely 
on that for the case I described in the original report. (That said, I 
think it would only be an issue for some truly esoteric configurations.)

On the other hand, I think I like the idea of having grep be aware of 
connection-local variables even better. That's more flexible, and also 
should work for the reverse case: if you call rgrep from a Tramp file 
buffer, but change the search directory to a local path, rgrep uses 
POSIX shell-quoting. It should use MS-Windows shell-quoting in that case 
(since it's running the command on the local Windows system).