Added documentation for schema upgrade.

Summary:
Documentation describes how to use the script to upgrade schema.

Test Plan:
Generated the documentation and it looked good.

Reviewed By: epriestley
Reviewers: epriestley
CC: jungejason, epriestley
Differential Revision: 124

src/docs/configuration_guide.diviner

@@ -16,12 +16,8 @@ schemata into it. First, load the initial database schema.
 
   mysql -uroot < path/to/phabricator/resources/sql/init/initialize.sql
 
-Next, load each of the database patches in order. (One day this will be
+After this you need to upgrade the schema see @{article:Upgrading Schema},
-better.)
+but you need to finish the rest of the configuration first.
-
-  mysql -uroot < path/to/phabricator/resources/sql/patches/000.project.sql
-  mysql -uroot < path/to/phabricator/resources/sql/patches/001...
-  ...
 
 = Configuring Apache =
 
@@ -119,3 +115,8 @@ configuring Apache:
 
 Now, look through ##default.conf.php## and override any options you want to
 change by providing overrides in ##myconfig.conf.php##.
+
+= Upgrading Schema =
+
+After you have configured Phabricator, you need to upgrade the database
+schema, see @{article:Upgrading Schema}

src/docs/upgrade_schema.diviner

@@ -0,0 +1,32 @@
+@title Upgrading Schema
+@group config
+
+This document descibes how to upgrade the database schema.
+
+= Prerequisites =
+
+This document assumes you've already initialized the MySQL database and
+configured your Phabricator environment. If you haven't, see
+@{article:Configuration Guide}.
+
+= Loading patches =
+
+If you are doing this for the first time to a freshly installed MySQL database,
+run the following command:
+
+  PHABRICATOR_ENV=<your_config> php path/to/phabricator/scripts/sql/upgrade_schema.php 0
+
+This will install all the patches starting from 0. Running this script will
+store the information of the latest installed patch in the Phabricator database.
+Next time you want to upgrade your schema, just run:
+
+  PHABRICATOR_ENV=<your_config> php path/to/phabricator/scripts/sql/upgrade_schema.php
+
+This will install all the patches that are new since the last time you ran
+this script.
+
+If you need to upgrade the schema starting from a specific patch, just run:
+
+  PHABRICATOR_ENV=<your_config> php path/to/phabricator/scripts/sql/upgrade_schema.php <patch_number>
+
+However, this isn't usually needed.