Don't implement SVN over HTTP

Summary:
Ref T2230. As far as I can tell, getting SVN working over HTTP is incredibly complicated. It's all DAV-based and doesn't appear to have any kind of binary we can just execute and pass requests through to. Don't support it for now.

  - Disable it in the UI.
  - Make sure all the error messages are reasonable.

Test Plan: Tried to HTTP an SVN repo. Tried to clone a Git repo with SVN, got a good error message.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2230

Differential Revision: https://secure.phabricator.com/D7562

src/applications/diffusion/controller/DiffusionRepositoryEditHostingController.php

@@ -126,6 +126,9 @@ final class DiffusionRepositoryEditHostingController
     $request = $this->getRequest();
     $user = $request->getUser();
 
+    $type = $repository->getVersionControlSystem();
+    $is_svn = ($type == PhabricatorRepositoryType::REPOSITORY_TYPE_SVN);
+
     $v_http_mode = $repository->getDetail(
       'serve-over-http',
       PhabricatorRepository::SERVE_OFF);
@@ -146,9 +149,11 @@ final class DiffusionRepositoryEditHostingController
       $type_http = PhabricatorRepositoryTransaction::TYPE_PROTOCOL_HTTP;
       $type_ssh = PhabricatorRepositoryTransaction::TYPE_PROTOCOL_SSH;
 
-      $xactions[] = id(clone $template)
-        ->setTransactionType($type_http)
-        ->setNewValue($v_http_mode);
+      if (!$is_svn) {
+        $xactions[] = id(clone $template)
+          ->setTransactionType($type_http)
+          ->setNewValue($v_http_mode);
+      }
 
       $xactions[] = id(clone $template)
         ->setTransactionType($type_ssh)
@@ -232,6 +237,18 @@ final class DiffusionRepositoryEditHostingController
             PhabricatorRepository::SERVE_READWRITE),
           $rw_message);
 
+    if ($is_svn) {
+      $http_control = id(new AphrontFormMarkupControl())
+        ->setLabel(pht('HTTP'))
+        ->setValue(
+          phutil_tag(
+            'em',
+            array(),
+            pht(
+              'Phabricator does not currently support HTTP access to '.
+              'Subversion repositories.')));
+    }
+
     $form = id(new AphrontFormView())
       ->setUser($user)
       ->appendRemarkupInstructions(