make sure we only cache resources which contain a svn revision

like we do in the VCS driver.

Closes #7158

src/Composer/Repository/Vcs/SvnDriver.php

@@ -115,19 +115,29 @@ class SvnDriver extends VcsDriver
         return null;
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    protected function shouldCache($identifier)
+    {
+        return $this->cache && preg_match('{@\d+$}', $identifier);
+    }
+
     /**
      * {@inheritdoc}
      */
     public function getComposerInformation($identifier)
     {
         if (!isset($this->infoCache[$identifier])) {
-            if ($res = $this->cache->read($identifier.'.json')) {
+            if ($this->shouldCache($identifier) && $res = $this->cache->read($identifier.'.json')) {
                 return $this->infoCache[$identifier] = JsonFile::parseJson($res);
             }
 
             $composer = $this->getBaseComposerInformation($identifier);
 
-            $this->cache->write($identifier.'.json', json_encode($composer));
+            if ($this->shouldCache($identifier)) {
+                $this->cache->write($identifier.'.json', json_encode($composer));
+            }
 
             $this->infoCache[$identifier] = $composer;
         }