bug#8968: arc-mode 7z writing support

[Jason Rumney]

Eli Zaretskii <eliz@gnu.org> writes:

> I don't have a definitive answer.  All I know is that arc-mode could
> not handle certain archives that I could handle with a 7z.exe
> downloaded for comparison.  I then researched this issue and found out
> that those archives used a newer format that the Free Software
> variants of 7z did not support.

Were these archives .rar archives?  If so, it is an older format, not a
newer one, and not the core format of 7z, just supported for
completeness.  If not, then this is an issue that I cannot find any
information about - perhaps you could point us to the information so we
can stop recommending 7-Zip to others.

> on fencepost didn't support it.  And the reason was that the newer
> formats used code that wasn't Free Software and whose sources were not
> available even under non-Free licenses.

Even the non-Free unRAR source is available, it just comes with
unacceptable restrictions on its use. So I'd be interested in what this
new format is.