Warning about the UNIX permissions lost if unzip command is not installed.

Some packages provide (such as Symfony Panther or Dusk) executable files, but
as PHP's unzip extension does not handle UNIX permissions, those files will
lose their executable ones.

src/Composer/Downloader/ZipDownloader.php

@@ -69,7 +69,8 @@ class ZipDownloader extends ArchiveDownloader
 
             if (!self::$isWindows && !self::$hasSystemUnzip) {
                 $this->io->writeError("<warning>As there is no 'unzip' command installed zip files are being unpacked using the PHP zip extension.</warning>");
-                $this->io->writeError("<warning>This may cause invalid reports of corrupted archives. Installing 'unzip' may remediate them.</warning>");
+                $this->io->writeError("<warning>This may cause invalid reports of corrupted archives. Besides, any UNIX permissions (e.g. executable) defined in the archives will be lost.</warning>");
+                $this->io->writeError("<warning>Installing 'unzip' may remediate them.</warning>");
             }
         }