Use unique identifier for meme hash

Summary: "a:" plus "b" and "a" plus ":b" created the same ID.

Test Plan: Created a meme.

Reviewers: DeedyDas, epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D4631

src/applications/macro/controller/PhabricatorMacroMemeController.php

@@ -20,7 +20,7 @@ final class PhabricatorMacroMemeController
 
     $upper_text = strtoupper($upper_text);
     $lower_text = strtoupper($lower_text);
-    $mixed_text = $upper_text.":".$lower_text;
+    $mixed_text = md5($upper_text).":".md5($lower_text);
     $hash = "meme".hash("sha256", $mixed_text);
     $xform = id(new PhabricatorTransformedFile())
       ->loadOneWhere('originalphid=%s and transform=%s',