Add a bin/hunks script to manage migrations of hunk data

Summary:
Ref T4045. Ref T5179. While we'll eventually need to force a migration, we can let installs (particularly large installs) do an online migration for now. This moves hunks to the new storage format one at a time.

(Note that nothing writes to the new store yet, so this is the only way to populate it.)

WARNING: Installs, don't run this yet! It won't compress the data. Wait until it can also do compression.

Test Plan: Added a `break;` after migrating one row and moved a few rows over. Spot checked them in the database and viewed the affected diffs.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4045, T5179

Differential Revision: https://secure.phabricator.com/D9291

scripts/setup/manage_hunks.php

@@ -0,0 +1,21 @@
+#!/usr/bin/env php
+<?php
+
+$root = dirname(dirname(dirname(__FILE__)));
+require_once $root.'/scripts/__init_script__.php';
+
+$args = new PhutilArgumentParser($argv);
+$args->setTagline('manage hunks');
+$args->setSynopsis(<<<EOSYNOPSIS
+**hunks** __command__ [__options__]
+    Manage Differential hunk storage.
+
+EOSYNOPSIS
+  );
+$args->parseStandardArguments();
+
+$workflows = id(new PhutilSymbolLoader())
+  ->setAncestorClass('PhabricatorHunksManagementWorkflow')
+  ->loadObjects();
+$workflows[] = new PhutilHelpArgumentWorkflow();
+$args->parseWorkflows($workflows);