Add a setup warning about missing 'fileinfo'

Summary:
See <https://github.com/facebook/phabricator/issues/320>. We have a soft dependency on 'fileinfo', which we try to recover from (with `file`) but won't be able to on Windows and apparently FreeBSD systems. Since users can ignore setup checks anyway now, just raise a warning during install.

I believe almost all installs should have this extension, it has been part of the core for a long time.

Test Plan: Faked setup failure, looked at warning. "Solved" setup failure, saw it go away.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D5952

src/__phutil_library_map__.php

@@ -1383,6 +1383,7 @@ phutil_register_library_map(array(
     'PhabricatorSetupCheckExtensions' => 'applications/config/check/PhabricatorSetupCheckExtensions.php',
     'PhabricatorSetupCheckExtraConfig' => 'applications/config/check/PhabricatorSetupCheckExtraConfig.php',
     'PhabricatorSetupCheckFacebook' => 'applications/config/check/PhabricatorSetupCheckFacebook.php',
+    'PhabricatorSetupCheckFileinfo' => 'applications/config/check/PhabricatorSetupCheckFileinfo.php',
     'PhabricatorSetupCheckGD' => 'applications/config/check/PhabricatorSetupCheckGD.php',
     'PhabricatorSetupCheckImagemagick' => 'applications/config/check/PhabricatorSetupCheckImagemagick.php',
     'PhabricatorSetupCheckInvalidConfig' => 'applications/config/check/PhabricatorSetupCheckInvalidConfig.php',
@@ -3114,6 +3115,7 @@ phutil_register_library_map(array(
     'PhabricatorSetupCheckExtensions' => 'PhabricatorSetupCheck',
     'PhabricatorSetupCheckExtraConfig' => 'PhabricatorSetupCheck',
     'PhabricatorSetupCheckFacebook' => 'PhabricatorSetupCheck',
+    'PhabricatorSetupCheckFileinfo' => 'PhabricatorSetupCheck',
     'PhabricatorSetupCheckGD' => 'PhabricatorSetupCheck',
     'PhabricatorSetupCheckImagemagick' => 'PhabricatorSetupCheck',
     'PhabricatorSetupCheckInvalidConfig' => 'PhabricatorSetupCheck',

src/applications/config/check/PhabricatorSetupCheckFileinfo.php

@@ -0,0 +1,17 @@
+<?php
+
+final class PhabricatorSetupCheckFileinfo extends PhabricatorSetupCheck {
+
+  protected function executeChecks() {
+    if (!extension_loaded('fileinfo')) {
+      $message = pht(
+        "The 'fileinfo' extension is not installed. Without 'fileinfo', ".
+        "support, Phabricator may not be able to determine the MIME types ".
+        "of uploaded files.");
+
+      $this->newIssue('extension.fileinfo')
+        ->setName(pht("Missing 'fileinfo' Extension"))
+        ->setMessage($message);
+    }
+  }
+}