Subject: 29.1; dired-guess-default command for tar.zst file fails

From: Michael Eliachevitch <[email-masked]>
Date: Fri, 13 Oct 2023 11:54:00 +0000

I tried to extract the attached zstandard-compressed tar archive
`testdir.tar.zst' using the dired-guess-default suggested shell command,
which is

    unzstd -c %i | tar -xf -

It fails with the message

    zstd: can't stat %i : No such file or directory -- ignored
    tar: This does not look like a tar archive
    tar: testdir.tar.zst: Not found in archive

What instead works is using the command

  tar --use-compress-program=unzstd -xvf

My GNU tar version also is able to automatically detect zstandard files,
so basically just "tar -xvf" is suffisient, but the version with
"--use-compress-program=unzstd" is backwards-compatible to older tar
versions.

I suggest fixing that in `dired-guess-shell-alist-default'. Though there
might be tar versions out there which don't support
`--use-compress-program' (I don't know), then maybe a piping solution
might be better, but that should be done in a way that avoid the above
error (not sure what actually causes it).

I use GNU tar version 1.35 and unzstd version v1.5.5.
---

In GNU Emacs 29.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38,
cairo version 1.17.8)
System Description: Arch Linux

Configured using:
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