Rename "PhabricatorHash::digest()" to "weakDigest()"

Summary: Ref T12509. This encourages code to move away from HMAC+SHA1 by making the method name more obviously undesirable.

Test Plan: `grep`, browsed around.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12509

Differential Revision: https://secure.phabricator.com/D17632

src/applications/files/engine/PhabricatorChunkedFileStorageEngine.php

@@ -102,7 +102,7 @@ final class PhabricatorChunkedFileStorageEngine
   }
 
   public static function getChunkedHashForInput($input) {
-    $rehash = PhabricatorHash::digest($input);
+    $rehash = PhabricatorHash::weakDigest($input);
 
     // Add a suffix to identify this as a chunk hash.
     $rehash = substr($rehash, 0, -2).'-C';