Add --gc flag to clear-cache command and ability to GC vcs/repo caches

doc/03-cli.md

@@ -902,6 +902,10 @@ performance.
 
 Deletes all content from Composer's cache directories.
 
+### Options
+
+* **--gc:** Only run garbage collection, not a full cache clear
+
 ## licenses
 
 Lists the name, version and license of every package installed. Use

src/Composer/Cache.php

@@ -339,6 +339,25 @@ public function gc(int $ttl, int $maxSize)
         return false;
     }
 
+    public function gcVcsCache(int $ttl): bool
+    {
+        if ($this->isEnabled()) {
+            $expire = new \DateTime();
+            $expire->modify('-'.$ttl.' seconds');
+
+            $finder = Finder::create()->in($this->root)->directories()->depth(0)->date('until '.$expire->format('Y-m-d H:i:s'));
+            foreach ($finder as $file) {
+                $this->filesystem->removeDirectory($file->getPathname());
+            }
+
+            self::$cacheCollected = true;
+
+            return true;
+        }
+
+        return false;
+    }
+
     /**
      * @param string $file
      *

src/Composer/Command/ClearCacheCommand.php

@@ -15,6 +15,7 @@
 use Composer\Cache;
 use Composer\Factory;
 use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 
 /**
@@ -31,6 +32,9 @@ protected function configure(): void
             ->setName('clear-cache')
             ->setAliases(array('clearcache', 'cc'))
             ->setDescription('Clears composer\'s internal package cache.')
+            ->setDefinition(array(
+                new InputOption('gc', null, InputOption::VALUE_NONE, 'Only run garbage collection, not a full cache clear'),
+            ))
             ->setHelp(
                 <<<EOT
 The <info>clear-cache</info> deletes all cached packages from composer's
@@ -55,6 +59,11 @@ protected function execute(InputInterface $input, OutputInterface $output): int
         );
 
         foreach ($cachePaths as $key => $cachePath) {
+            // only individual dirs get garbage collected
+            if ($key === 'cache-dir' && $input->getOption('gc')) {
+                continue;
+            }
+
             $cachePath = realpath($cachePath);
             if (!$cachePath) {
                 $io->writeError("<info>Cache directory does not exist ($key): $cachePath</info>");
@@ -69,11 +78,26 @@ protected function execute(InputInterface $input, OutputInterface $output): int
                 continue;
             }
 
-            $io->writeError("<info>Clearing cache ($key): $cachePath</info>");
-            $cache->clear();
+            if ($input->getOption('gc')) {
+                $io->writeError("<info>Garbage-collecting cache ($key): $cachePath</info>");
+                if ($key === 'cache-files-dir') {
+                    $cache->gc($config->get('cache-files-ttl'), $config->get('cache-files-maxsize'));
+                } elseif ($key === 'cache-repo-dir') {
+                    $cache->gc($config->get('cache-ttl'), 1024*1024*1024 /* 1GB, this should almost never clear anything that is not outdated */);
+                } elseif ($key === 'cache-vcs-dir') {
+                    $cache->gcVcsCache($config->get('cache-ttl'));
+                }
+            } else {
+                $io->writeError("<info>Clearing cache ($key): $cachePath</info>");
+                $cache->clear();
+            }
         }
 
-        $io->writeError('<info>All caches cleared.</info>');
+        if ($input->getOption('gc')) {
+            $io->writeError('<info>All caches garbage-collected.</info>');
+        } else {
+            $io->writeError('<info>All caches cleared.</info>');
+        }
 
         return 0;
     }