Keep --installed option for BC

src/Composer/Command/ShowCommand.php

@@ -53,6 +53,7 @@ class ShowCommand extends BaseCommand
                 new InputArgument('package', InputArgument::OPTIONAL, 'Package to inspect'),
                 new InputArgument('version', InputArgument::OPTIONAL, 'Version or version constraint to inspect'),
                 new InputOption('all', null, InputOption::VALUE_NONE, 'List all packages'),
+                new InputOption('installed', 'i', InputOption::VALUE_NONE, 'List installed packages only (enabled by default, only present for BC).'),
                 new InputOption('platform', 'p', InputOption::VALUE_NONE, 'List platform packages only'),
                 new InputOption('available', 'a', InputOption::VALUE_NONE, 'List available packages only'),
                 new InputOption('self', 's', InputOption::VALUE_NONE, 'Show the root package information'),
@@ -79,6 +80,10 @@ EOT
         $composer = $this->getComposer(false);
         $io = $this->getIO();
 
+        if ($input->getOption('installed')) {
+            $io->writeError('<warning>You are using the deprecated option "installed". Only installed packages are shown by default now. The --all option can be used to show all packages.</warning>');
+        }
+
         if ($input->getOption('tree') && ($input->getOption('all') || $input->getOption('available'))) {
             $io->writeError('The --tree (-t) option is not usable in combination with --all or --available (-a)');
             return;