bug#44753: 27.1; arc-mode does not extract marked files

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Vladimir Nikishkin <lockywolf@gmail.com>,  44753@debbugs.gnu.org
> Date: Fri, 20 Nov 2020 10:09:23 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > We need first to add a capability to extract archive members to files.
> 
> This was added to the trunk in August.

You are right, I forgot about that, sorry.

However, the implementation of archive-copy-file doesn't seem to be
easily scalable to what Vladimir requested.  It is also sub-optimal
(to say the least) to extract files by going through a temporary
buffer, since every archive type has some way of extracting files
directly.  If nothing else, this will cause serious problems with
encoding, especially when several files are extracted at once that
happen to be encoded differently.  And the speed will also be much
slower than if we use the archiver program to do the extraction.