Added instructions to patch submission form.

src/applications/differential/controller/DifferentialDiffCreateController.php

@@ -53,19 +53,27 @@ final class DifferentialDiffCreateController extends DifferentialController {
 
     $cancel_uri = $this->getApplicationURI();
 
-    $form
-      ->setAction('/differential/diff/create/')
-      ->setEncType('multipart/form-data')
-      ->setUser($request->getUser())
-      ->appendInstructions(
-        pht(
+    if (PhabricatorEnv::getEnvConfig('patch_guidelines.file') !== null) {
+      $webroot = dirname(phutil_get_library_root('phabricator')).'/webroot/';
+      $instructions = phutil_safe_html(
+        FileSystem::readFile($webroot .
+          PhabricatorEnv::getEnvConfig('patch_guidelines.file')));
+    } else {
+      $innstructions = pht(
           'The best way to create a Differential diff is by using %s, but you '.
           'can also just paste a diff (for example, from %s, %s or %s) into '.
           'this box, or upload a diff file.',
           $arcanist_link,
           phutil_tag('tt', array(), 'svn diff'),
           phutil_tag('tt', array(), 'git diff'),
-          phutil_tag('tt', array(), 'hg diff')))
+          phutil_tag('tt', array(), 'hg diff'));
+    }
+
+    $form
+      ->setAction('/differential/diff/create/')
+      ->setEncType('multipart/form-data')
+      ->setUser($request->getUser())
+      ->appendInstructions($instructions)
       ->appendChild(
         id(new AphrontFormTextAreaControl())
           ->setLabel(pht('Raw Diff'))