Issue and solution reported by user jooomlaa at
https://forum.joomla.de/thread/6201-vermutl-fehler-in-libraries-vendor-joomla-archive-src-archive-php-beim-entpacken/

Summary of Changes

• Correct target path of extracted gzip or gz archives.

Testing Instructions

• Joomla staging with template protostar.

• Configuration: error_reporting => Maximum

• Configuration: debug => Yes

• Crréate a folder /tmp/source/

• Put a gzip file in it that shall be extracted.
  e.g. https://forum.joomla.de/core/attachment/2757-namen-fr-fenja-txt-gzip/

• Enter following code in protostar index.php after line defined('_JEXEC') or die;

use Joomla\Archive\Archive;

$fileName = 'Namen_fr-Fenja.txt.gzip';

$archive = new Archive(array('tmp_path' => JFactory::getConfig()->get('tmp_path')));

$archiveName = JPATH_SITE . '/tmp/source/' . $fileName;
$extractDir = JPATH_SITE . '/tmp/target';
$archive->extract($archiveName, $extractDir);
exit;

• Pay attention that folder /tmp/target doesn't exist before test.

• Open protostar page in frontend that runs the code.

Expected result

• A new folder /tmp/target/ with extracted file Namen_fr-Fenja in it

Actual result

• A temporary file like gzip5b83db746bab9 in /tmp/
• error page

Joomla\Filesystem\File::copy: Copy failed.
.../libraries/vendor/joomla/filesystem/src/File.php:94

Call stack
--
# | Function | Location
1 | () | JROOT/libraries/vendor/joomla/filesystem/src/File.php:94
2 | Joomla\Filesystem\File::copy() | JROOT/libraries/vendor/joomla/archive/src/Archive.php:115

Apply patch

• Try again.
• Beware that protostar page is just empty because of exit; in code above (= OK).
• A new folder /tmp/target/ with extracted file Namen_fr-Fenja in it
• The temporary file like gzip5b83db746bab9 is not present in folder /tmp/