Support SVN pre-commit hoooks

Summary:
Ref T4189. This adds SVN support, which was a little more messy than I though. Principally, we can not use `PHABRICATOR_USER` for Subversion, because it strips away the entire environment for "security reasons".

Instead, use `--tunnel-user` plus `svnlook author` to figure out the author.

Also fix "ssh://" clone URIs, which needs to be "svn+ssh://".

Test Plan:
  - Made SVN commits through the hook.
  - Made Git commits, too, to make sure I didn't break anything.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4189

Differential Revision: https://secure.phabricator.com/D7683

src/applications/diffusion/controller/DiffusionRepositoryController.php

@@ -173,7 +173,12 @@ final class DiffusionRepositoryController extends DiffusionController {
       $serve_ssh = $repository->getServeOverSSH();
       if ($serve_ssh !== $serve_off) {
         $uri = new PhutilURI(PhabricatorEnv::getProductionURI($repo_path));
-        $uri->setProtocol('ssh');
+
+        if ($repository->isSVN()) {
+          $uri->setProtocol('svn+ssh');
+        } else {
+          $uri->setProtocol('ssh');
+        }
 
         $ssh_user = PhabricatorEnv::getEnvConfig('diffusion.ssh-user');
         if ($ssh_user) {