diff --git a/.gitignore b/.gitignore
index d2c98d9..415be55 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,37 +1,38 @@
 # NOTE: Thinking about adding files created by your operating system, IDE,
 # or text editor here? Don't! Add them to your per-user .gitignore instead.
 
 # Diviner
 /docs/
 /.divinercache/
 
 # XHPAST
 /support/xhpast/*.a
 /support/xhpast/*.o
 /support/xhpast/parser.yacc.output
 /support/xhpast/node_names.hpp
 /support/xhpast/xhpast
 /src/parser/xhpast/bin/xhpast
 
 ## NOTE: Don't .gitignore these files! Even though they're build artifacts, we
 ## want to check them in so users can build xhpast without flex/bison.
 # /support/xhpast/parser.yacc.cpp
 # /support/xhpast/parser.yacc.hpp
 # /support/xhpast/scanner.lex.cpp
 # /support/xhpast/scanner.lex.hpp
 
 # This is an OS X build artifact.
 /support/xhpast/xhpast.dSYM
 
 # This is a Windows build artifact.
 /support/xhpast/xhpast.exe
 
 # libphutil
 /src/.phutil_module_cache
 /support/phutiltestlib/.phutil_module_cache
 
 # This file overrides "default.pem" if present.
 /resources/ssl/custom.pem
 
 # User extensions
+/externals/includes/*
 /src/extensions/*
diff --git a/externals/includes/README b/externals/includes/README
new file mode 100644
index 0000000..4b2f77f
--- /dev/null
+++ b/externals/includes/README
@@ -0,0 +1,3 @@
+This directory is added to the PHP include path. You can symlink things here
+if you have control over directory setup but not over PHP configuration (for
+instance, in Homebrew).
\ No newline at end of file
diff --git a/scripts/__init_script__.php b/scripts/__init_script__.php
index 2fb893f..12de287 100644
--- a/scripts/__init_script__.php
+++ b/scripts/__init_script__.php
@@ -1,95 +1,101 @@
 <?php
 
 function __phutil_init_script__() {
   // Adjust the runtime language configuration to be reasonable and inline with
   // expectations. We do this first, then load libraries.
 
   // There may be some kind of auto-prepend script configured which starts an
   // output buffer. Discard any such output buffers so messages can be sent to
   // stdout (if a user wants to capture output from a script, there are a large
   // number of ways they can accomplish it legitimately; historically, we ran
   // into this on only one install which had some bizarre configuration, but it
   // was difficult to diagnose because the symptom is "no messages of any
   // kind").
   while (ob_get_level() > 0) {
     ob_end_clean();
   }
 
   error_reporting(E_ALL | E_STRICT);
 
   $config_map = array(
     // Always display script errors. Without this, they may not appear, which is
     // unhelpful when users encounter a problem. On the web this is a security
     // concern because you don't want to expose errors to clients, but in a
     // script context we always want to show errors.
     'display_errors'              => true,
 
-    // Send script error messages to the server's error_log setting.
+    // Send script error messages to the server's `error_log` setting.
     'log_errors'                  => true,
 
     // Set the error log to the default, so errors go to stderr. Without this
     // errors may end up in some log, and users may not know where the log is
     // or check it.
     'error_log'                   => null,
 
     // XDebug raises a fatal error if the call stack gets too deep, but the
     // default setting is 100, which we may exceed legitimately with module
     // includes (and in other cases, like recursive filesystem operations
     // applied to 100+ levels of directory nesting). Stop it from triggering:
     // we explicitly limit recursive algorithms which should be limited.
 
     // After Feb 2014, XDebug inteprets a value of 0 to mean "do not allow any
     // function calls". Previously, 0 effectively disabled this check. For
     // context, see T5027.
     'xdebug.max_nesting_level'    => PHP_INT_MAX,
 
     // Don't limit memory, doing so just generally just prevents us from
     // processing large inputs without many tangible benefits.
     'memory_limit'                => -1,
   );
 
   foreach ($config_map as $config_key => $config_value) {
     ini_set($config_key, $config_value);
   }
 
   if (!ini_get('date.timezone')) {
     // If the timezone isn't set, PHP issues a warning whenever you try to parse
     // a date (like those from Git or Mercurial logs), even if the date contains
     // timezone information (like "PST" or "-0700") which makes the
     // environmental timezone setting is completely irrelevant. We never rely on
     // the system timezone setting in any capacity, so prevent PHP from flipping
     // out by setting it to a safe default (UTC) if it isn't set to some other
     // value.
     date_default_timezone_set('UTC');
   }
 
+  // Adjust `include_path`.
+  ini_set('include_path', implode(PATH_SEPARATOR, array(
+    dirname(dirname(__FILE__)).'/externals/includes',
+    ini_get('include_path'),
+  )));
+
   // Disable the insanely dangerous XML entity loader by default.
   if (function_exists('libxml_disable_entity_loader')) {
     libxml_disable_entity_loader(true);
   }
 
   // Now, load libphutil.
 
   $root = dirname(dirname(__FILE__));
   require_once $root.'/src/__phutil_library_init__.php';
 
   PhutilErrorHandler::initialize();
 
   // If possible, install a signal handler for SIGHUP which prints the current
   // backtrace out to a named file. This is particularly helpful in debugging
   // hung/spinning processes.
   if (function_exists('pcntl_signal')) {
     pcntl_signal(SIGHUP, '__phutil_signal_handler__');
   }
 }
 
 function __phutil_signal_handler__($signal_number) {
   $e = new Exception();
   $pid = getmypid();
   // Some phabricator daemons may not be attached to a terminal.
   Filesystem::writeFile(
     sys_get_temp_dir().'/phabricator_backtrace_'.$pid,
     $e->getTraceAsString());
 }
 
 __phutil_init_script__();