Merge pull request #8151 from naderman/self-update-target

Allow overriding self-update target file with env var COMPOSER_SELF_UPDATE_TARGET

src/Composer/Command/SelfUpdateCommand.php

@@ -351,6 +351,10 @@ TAGSPUBKEY
                 @copy($localFilename, $backupTarget);
             }
 
+            if ($targetFilename = getenv('COMPOSER_SELF_UPDATE_TARGET')) {
+                $localFilename = realpath($targetFilename) ?: $targetFilename;
+            }
+
             rename($newFilename, $localFilename);
 
             return null;