composer.patch

diff --git a/src/Composer/Config.php b/src/Composer/Config.php
index 087949e..ec6f3e1 100644
--- a/src/Composer/Config.php
+++ b/src/Composer/Config.php
@@ -58,6 +58,9 @@ class Config
         // load defaults
         $this->config = static::$defaultConfig;
         $this->repositories = static::$defaultRepositories;
+        if (getenv("COMPOSER_REPOSITORY_URL")) {
+            $this->repositories['packagist']['url'] = getenv("COMPOSER_REPOSITORY_URL");
+        }
     }
 
     public function setConfigSource(ConfigSourceInterface $source)