diff --git a/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php
index 52a8478fdc..6de16e723d 100644
--- a/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionGitSSHWorkflow.php
@@ -1,38 +1,48 @@
 <?php
 
 abstract class DiffusionGitSSHWorkflow
   extends DiffusionSSHWorkflow
   implements DiffusionRepositoryClusterEngineLogInterface {
 
   protected function writeError($message) {
     // Git assumes we'll add our own newlines.
     return parent::writeError($message."\n");
   }
 
   public function writeClusterEngineLogMessage($message) {
     parent::writeError($message);
     $this->getErrorChannel()->update();
   }
 
   protected function identifyRepository() {
     $args = $this->getArgs();
     $path = head($args->getArg('dir'));
     return $this->loadRepositoryWithPath(
       $path,
       PhabricatorRepositoryType::REPOSITORY_TYPE_GIT);
   }
 
   protected function waitForGitClient() {
     $io_channel = $this->getIOChannel();
 
     // If we don't wait for the client to close the connection, `git` will
     // consider it an early abort and fail. Sit around until Git is comfortable
     // that it really received all the data.
     while ($io_channel->isOpenForReading()) {
       $io_channel->update();
       $this->getErrorChannel()->flush();
       PhutilChannel::waitForAny(array($io_channel));
     }
   }
 
+  protected function raiseWrongVCSException(
+    PhabricatorRepository $repository) {
+    throw new Exception(
+      pht(
+        'This repository ("%s") is not a Git repository. Use "%s" to '.
+        'interact with this repository.',
+        $repository->getDisplayName(),
+        $repository->getVersionControlSystem()));
+  }
+
 }
diff --git a/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php
index 15dd9d7c6b..4508ae53da 100644
--- a/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php
@@ -1,122 +1,132 @@
 <?php
 
 final class DiffusionMercurialServeSSHWorkflow
   extends DiffusionMercurialSSHWorkflow {
 
   protected $didSeeWrite;
 
   protected function didConstruct() {
     $this->setName('hg');
     $this->setArguments(
       array(
         array(
           'name' => 'repository',
           'short' => 'R',
           'param' => 'repo',
         ),
         array(
           'name' => 'stdio',
         ),
         array(
           'name' => 'command',
           'wildcard' => true,
         ),
       ));
   }
 
   protected function identifyRepository() {
     $args = $this->getArgs();
     $path = $args->getArg('repository');
     return $this->loadRepositoryWithPath(
       $path,
       PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL);
   }
 
   protected function executeRepositoryOperations() {
     $repository = $this->getRepository();
     $args = $this->getArgs();
 
     if (!$args->getArg('stdio')) {
       throw new Exception(pht('Expected `%s`!', 'hg ... --stdio'));
     }
 
     if ($args->getArg('command') !== array('serve')) {
       throw new Exception(pht('Expected `%s`!', 'hg ... serve'));
     }
 
     if ($this->shouldProxy()) {
       $command = $this->getProxyCommand();
     } else {
       $command = csprintf(
         'hg -R %s serve --stdio',
         $repository->getLocalPath());
     }
     $command = PhabricatorDaemon::sudoCommandAsDaemonUser($command);
 
     $future = id(new ExecFuture('%C', $command))
       ->setEnv($this->getEnvironment());
 
     $io_channel = $this->getIOChannel();
     $protocol_channel = new DiffusionMercurialWireClientSSHProtocolChannel(
       $io_channel);
 
     $err = id($this->newPassthruCommand())
       ->setIOChannel($protocol_channel)
       ->setCommandChannelFromExecFuture($future)
       ->setWillWriteCallback(array($this, 'willWriteMessageCallback'))
       ->execute();
 
     // TODO: It's apparently technically possible to communicate errors to
     // Mercurial over SSH by writing a special "\n<error>\n-\n" string. However,
     // my attempt to implement that resulted in Mercurial closing the socket and
     // then hanging, without showing the error. This might be an issue on our
     // side (we need to close our half of the socket?), or maybe the code
     // for this in Mercurial doesn't actually work, or maybe something else
     // is afoot. At some point, we should look into doing this more cleanly.
     // For now, when we, e.g., reject writes for policy reasons, the user will
     // see "abort: unexpected response: empty string" after the diagnostically
     // useful, e.g., "remote: This repository is read-only over SSH." message.
 
     if (!$err && $this->didSeeWrite) {
       $repository->writeStatusMessage(
         PhabricatorRepositoryStatusMessage::TYPE_NEEDS_UPDATE,
         PhabricatorRepositoryStatusMessage::CODE_OKAY);
     }
 
     return $err;
   }
 
   public function willWriteMessageCallback(
     PhabricatorSSHPassthruCommand $command,
     $message) {
 
     $command = $message['command'];
 
     // Check if this is a readonly command.
 
     $is_readonly = false;
     if ($command == 'batch') {
       $cmds = idx($message['arguments'], 'cmds');
       if (DiffusionMercurialWireProtocol::isReadOnlyBatchCommand($cmds)) {
         $is_readonly = true;
       }
     } else if (DiffusionMercurialWireProtocol::isReadOnlyCommand($command)) {
       $is_readonly = true;
     }
 
     if (!$is_readonly) {
       $this->requireWriteAccess();
       $this->didSeeWrite = true;
     }
 
     $raw_message = $message['raw'];
     if ($command == 'capabilities') {
       $raw_message = DiffusionMercurialWireProtocol::filterBundle2Capability(
         $raw_message);
     }
 
     // If we're good, return the raw message data.
     return $raw_message;
   }
 
+  protected function raiseWrongVCSException(
+    PhabricatorRepository $repository) {
+    throw new Exception(
+      pht(
+        'This repository ("%s") is not a Mercurial repository. Use "%s" to '.
+        'interact with this repository.',
+        $repository->getDisplayName(),
+        $repository->getVersionControlSystem()));
+  }
+
 }
diff --git a/src/applications/diffusion/ssh/DiffusionSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionSSHWorkflow.php
index 0115858832..0e5ad7bbe1 100644
--- a/src/applications/diffusion/ssh/DiffusionSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionSSHWorkflow.php
@@ -1,274 +1,280 @@
 <?php
 
 abstract class DiffusionSSHWorkflow extends PhabricatorSSHWorkflow {
 
   private $args;
   private $repository;
   private $hasWriteAccess;
   private $proxyURI;
   private $baseRequestPath;
 
   public function getRepository() {
     if (!$this->repository) {
       throw new Exception(pht('Repository is not available yet!'));
     }
     return $this->repository;
   }
 
   private function setRepository(PhabricatorRepository $repository) {
     $this->repository = $repository;
     return $this;
   }
 
   public function getArgs() {
     return $this->args;
   }
 
   public function getEnvironment() {
     $env = array(
       DiffusionCommitHookEngine::ENV_USER => $this->getUser()->getUsername(),
       DiffusionCommitHookEngine::ENV_REMOTE_PROTOCOL => 'ssh',
     );
 
     $remote_address = $this->getSSHRemoteAddress();
     if ($remote_address !== null) {
       $env[DiffusionCommitHookEngine::ENV_REMOTE_ADDRESS] = $remote_address;
     }
 
     return $env;
   }
 
   /**
    * Identify and load the affected repository.
    */
   abstract protected function identifyRepository();
   abstract protected function executeRepositoryOperations();
+  abstract protected function raiseWrongVCSException(
+    PhabricatorRepository $repository);
 
   protected function getBaseRequestPath() {
     return $this->baseRequestPath;
   }
 
   protected function writeError($message) {
     $this->getErrorChannel()->write($message);
     return $this;
   }
 
   protected function getCurrentDeviceName() {
     $device = AlmanacKeys::getLiveDevice();
     if ($device) {
       return $device->getName();
     }
 
     return php_uname('n');
   }
 
   protected function getTargetDeviceName() {
     // TODO: This should use the correct device identity.
     $uri = new PhutilURI($this->proxyURI);
     return $uri->getDomain();
   }
 
   protected function shouldProxy() {
     return (bool)$this->proxyURI;
   }
 
   protected function getProxyCommand() {
     $uri = new PhutilURI($this->proxyURI);
 
     $username = AlmanacKeys::getClusterSSHUser();
     if ($username === null) {
       throw new Exception(
         pht(
           'Unable to determine the username to connect with when trying '.
           'to proxy an SSH request within the Phabricator cluster.'));
     }
 
     $port = $uri->getPort();
     $host = $uri->getDomain();
     $key_path = AlmanacKeys::getKeyPath('device.key');
     if (!Filesystem::pathExists($key_path)) {
       throw new Exception(
         pht(
           'Unable to proxy this SSH request within the cluster: this device '.
           'is not registered and has a missing device key (expected to '.
           'find key at "%s").',
           $key_path));
     }
 
     $options = array();
     $options[] = '-o';
     $options[] = 'StrictHostKeyChecking=no';
     $options[] = '-o';
     $options[] = 'UserKnownHostsFile=/dev/null';
 
     // This is suppressing "added <address> to the list of known hosts"
     // messages, which are confusing and irrelevant when they arise from
     // proxied requests. It might also be suppressing lots of useful errors,
     // of course. Ideally, we would enforce host keys eventually.
     $options[] = '-o';
     $options[] = 'LogLevel=quiet';
 
     // NOTE: We prefix the command with "@username", which the far end of the
     // connection will parse in order to act as the specified user. This
     // behavior is only available to cluster requests signed by a trusted
     // device key.
 
     return csprintf(
       'ssh %Ls -l %s -i %s -p %s %s -- %s %Ls',
       $options,
       $username,
       $key_path,
       $port,
       $host,
       '@'.$this->getUser()->getUsername(),
       $this->getOriginalArguments());
   }
 
   final public function execute(PhutilArgumentParser $args) {
     $this->args = $args;
 
     $viewer = $this->getUser();
     $have_diffusion = PhabricatorApplication::isClassInstalledForViewer(
       'PhabricatorDiffusionApplication',
       $viewer);
     if (!$have_diffusion) {
       throw new Exception(
         pht(
           'You do not have permission to access the Diffusion application, '.
           'so you can not interact with repositories over SSH.'));
     }
 
     $repository = $this->identifyRepository();
     $this->setRepository($repository);
 
     $is_cluster_request = $this->getIsClusterRequest();
     $uri = $repository->getAlmanacServiceURI(
       $viewer,
       $is_cluster_request,
       array(
         'ssh',
       ));
 
     if ($uri) {
       $this->proxyURI = $uri;
     }
 
     try {
       return $this->executeRepositoryOperations();
     } catch (Exception $ex) {
       $this->writeError(get_class($ex).': '.$ex->getMessage());
       return 1;
     }
   }
 
   protected function loadRepositoryWithPath($path, $vcs) {
     $viewer = $this->getUser();
 
     $info = PhabricatorRepository::parseRepositoryServicePath($path, $vcs);
     if ($info === null) {
       throw new Exception(
         pht(
           'Unrecognized repository path "%s". Expected a path like "%s", '.
           '"%s", or "%s".',
           $path,
           '/diffusion/X/',
           '/diffusion/123/',
           '/source/thaumaturgy.git'));
     }
 
     $identifier = $info['identifier'];
     $base = $info['base'];
 
     $this->baseRequestPath = $base;
 
     $repository = id(new PhabricatorRepositoryQuery())
       ->setViewer($viewer)
       ->withIdentifiers(array($identifier))
       ->needURIs(true)
       ->executeOne();
     if (!$repository) {
       throw new Exception(
         pht('No repository "%s" exists!', $identifier));
     }
 
     $protocol = PhabricatorRepositoryURI::BUILTIN_PROTOCOL_SSH;
     if (!$repository->canServeProtocol($protocol, false)) {
       throw new Exception(
         pht(
           'This repository ("%s") is not available over SSH.',
           $repository->getDisplayName()));
     }
 
+    if ($repository->getVersionControlSystem() != $vcs) {
+      $this->raiseWrongVCSException($repository);
+    }
+
     return $repository;
   }
 
   protected function requireWriteAccess($protocol_command = null) {
     if ($this->hasWriteAccess === true) {
       return;
     }
 
     $repository = $this->getRepository();
     $viewer = $this->getUser();
 
     if ($viewer->isOmnipotent()) {
       throw new Exception(
         pht(
           'This request is authenticated as a cluster device, but is '.
           'performing a write. Writes must be performed with a real '.
           'user account.'));
     }
 
     $protocol = PhabricatorRepositoryURI::BUILTIN_PROTOCOL_SSH;
     if ($repository->canServeProtocol($protocol, true)) {
       $can_push = PhabricatorPolicyFilter::hasCapability(
         $viewer,
         $repository,
         DiffusionPushCapability::CAPABILITY);
       if (!$can_push) {
         throw new Exception(
           pht('You do not have permission to push to this repository.'));
       }
     } else {
       if ($protocol_command !== null) {
         throw new Exception(
           pht(
             'This repository is read-only over SSH (tried to execute '.
             'protocol command "%s").',
             $protocol_command));
       } else {
         throw new Exception(
           pht('This repository is read-only over SSH.'));
       }
     }
 
     $this->hasWriteAccess = true;
     return $this->hasWriteAccess;
   }
 
   protected function shouldSkipReadSynchronization() {
     $viewer = $this->getUser();
 
     // Currently, the only case where devices interact over SSH without
     // assuming user credentials is when synchronizing before a read. These
     // synchronizing reads do not themselves need to be synchronized.
     if ($viewer->isOmnipotent()) {
       return true;
     }
 
     return false;
   }
 
   protected function newPullEvent() {
     $viewer = $this->getViewer();
     $repository = $this->getRepository();
     $remote_address = $this->getSSHRemoteAddress();
 
     return id(new PhabricatorRepositoryPullEvent())
       ->setEpoch(PhabricatorTime::getNow())
       ->setRemoteAddress($remote_address)
       ->setRemoteProtocol('ssh')
       ->setPullerPHID($viewer->getPHID())
       ->setRepositoryPHID($repository->getPHID());
   }
 
 }
diff --git a/src/applications/diffusion/ssh/DiffusionSubversionServeSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionSubversionServeSSHWorkflow.php
index 3a8b516443..f2a932f2bb 100644
--- a/src/applications/diffusion/ssh/DiffusionSubversionServeSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionSubversionServeSSHWorkflow.php
@@ -1,452 +1,462 @@
 <?php
 
 /**
  * This protocol has a good spec here:
  *
  *   http://svn.apache.org/repos/asf/subversion/trunk/subversion/libsvn_ra_svn/protocol
  */
 final class DiffusionSubversionServeSSHWorkflow
   extends DiffusionSubversionSSHWorkflow {
 
   private $didSeeWrite;
 
   private $inProtocol;
   private $outProtocol;
 
   private $inSeenGreeting;
 
   private $outPhaseCount = 0;
 
   private $internalBaseURI;
   private $externalBaseURI;
   private $peekBuffer;
   private $command;
   private $isProxying;
 
   private function getCommand() {
     return $this->command;
   }
 
   protected function didConstruct() {
     $this->setName('svnserve');
     $this->setArguments(
       array(
         array(
           'name' => 'tunnel',
           'short' => 't',
         ),
       ));
   }
 
   protected function identifyRepository() {
     // NOTE: In SVN, we need to read the first few protocol frames before we
     // can determine which repository the user is trying to access. We're
     // going to peek at the data on the wire to identify the repository.
 
     $io_channel = $this->getIOChannel();
 
     // Before the client will send us the first protocol frame, we need to send
     // it a connection frame with server capabilities. To figure out the
     // correct frame we're going to start `svnserve`, read the frame from it,
     // send it to the client, then kill the subprocess.
 
     // TODO: This is pretty inelegant and the protocol frame will change very
     // rarely. We could cache it if we can find a reasonable way to dirty the
     // cache.
 
     $command = csprintf('svnserve -t');
     $command = PhabricatorDaemon::sudoCommandAsDaemonUser($command);
     $future = new ExecFuture('%C', $command);
     $exec_channel = new PhutilExecChannel($future);
     $exec_protocol = new DiffusionSubversionWireProtocol();
 
     while (true) {
       PhutilChannel::waitForAny(array($exec_channel));
       $exec_channel->update();
 
       $exec_message = $exec_channel->read();
       if ($exec_message !== null) {
         $messages = $exec_protocol->writeData($exec_message);
         if ($messages) {
           $message = head($messages);
           $raw = $message['raw'];
 
           // Write the greeting frame to the client.
           $io_channel->write($raw);
 
           // Kill the subprocess.
           $future->resolveKill();
           break;
         }
       }
 
       if (!$exec_channel->isOpenForReading()) {
         throw new Exception(
           pht(
             '%s subprocess exited before emitting a protocol frame.',
             'svnserve'));
       }
     }
 
     $io_protocol = new DiffusionSubversionWireProtocol();
     while (true) {
       PhutilChannel::waitForAny(array($io_channel));
       $io_channel->update();
 
       $in_message = $io_channel->read();
       if ($in_message !== null) {
         $this->peekBuffer .= $in_message;
         if (strlen($this->peekBuffer) > (1024 * 1024)) {
           throw new Exception(
             pht(
               'Client transmitted more than 1MB of data without transmitting '.
               'a recognizable protocol frame.'));
         }
 
         $messages = $io_protocol->writeData($in_message);
         if ($messages) {
           $message = head($messages);
           $struct = $message['structure'];
 
           // This is the:
           //
           //   ( version ( cap1 ... ) url ... )
           //
           // The `url` allows us to identify the repository.
 
           $uri = $struct[2]['value'];
           $path = $this->getPathFromSubversionURI($uri);
 
           return $this->loadRepositoryWithPath(
             $path,
             PhabricatorRepositoryType::REPOSITORY_TYPE_SVN);
         }
       }
 
       if (!$io_channel->isOpenForReading()) {
         throw new Exception(
           pht(
             'Client closed connection before sending a complete protocol '.
             'frame.'));
       }
 
       // If the client has disconnected, kill the subprocess and bail.
       if (!$io_channel->isOpenForWriting()) {
         throw new Exception(
           pht(
             'Client closed connection before receiving response.'));
       }
     }
   }
 
   protected function executeRepositoryOperations() {
     $repository = $this->getRepository();
 
     $args = $this->getArgs();
     if (!$args->getArg('tunnel')) {
       throw new Exception(pht('Expected `%s`!', 'svnserve -t'));
     }
 
     if ($this->shouldProxy()) {
       $command = $this->getProxyCommand();
       $this->isProxying = true;
       $cwd = null;
     } else {
       $command = csprintf(
         'svnserve -t --tunnel-user=%s',
         $this->getUser()->getUsername());
       $cwd = PhabricatorEnv::getEmptyCWD();
     }
 
     $command = PhabricatorDaemon::sudoCommandAsDaemonUser($command);
     $future = new ExecFuture('%C', $command);
 
     // If we're receiving a commit, svnserve will fail to execute the commit
     // hook with an unhelpful error if the CWD isn't readable by the user we
     // are sudoing to. Switch to a readable, empty CWD before running
     // svnserve. See T10941.
     if ($cwd !== null) {
       $future->setCWD($cwd);
     }
 
     $this->inProtocol = new DiffusionSubversionWireProtocol();
     $this->outProtocol = new DiffusionSubversionWireProtocol();
 
     $this->command = id($this->newPassthruCommand())
       ->setIOChannel($this->getIOChannel())
       ->setCommandChannelFromExecFuture($future)
       ->setWillWriteCallback(array($this, 'willWriteMessageCallback'))
       ->setWillReadCallback(array($this, 'willReadMessageCallback'));
 
     $this->command->setPauseIOReads(true);
 
     $err = $this->command->execute();
 
     if (!$err && $this->didSeeWrite) {
       $this->getRepository()->writeStatusMessage(
         PhabricatorRepositoryStatusMessage::TYPE_NEEDS_UPDATE,
         PhabricatorRepositoryStatusMessage::CODE_OKAY);
     }
 
     return $err;
   }
 
   public function willWriteMessageCallback(
     PhabricatorSSHPassthruCommand $command,
     $message) {
 
     $proto = $this->inProtocol;
     $messages = $proto->writeData($message);
 
     $result = array();
     foreach ($messages as $message) {
       $message_raw = $message['raw'];
       $struct = $message['structure'];
 
       if (!$this->inSeenGreeting) {
         $this->inSeenGreeting = true;
 
         // The first message the client sends looks like:
         //
         //   ( version ( cap1 ... ) url ... )
         //
         // We want to grab the URL, load the repository, make sure it exists and
         // is accessible, and then replace it with the location of the
         // repository on disk.
 
         $uri = $struct[2]['value'];
         $struct[2]['value'] = $this->makeInternalURI($uri);
 
         $message_raw = $proto->serializeStruct($struct);
       } else if (isset($struct[0]) && $struct[0]['type'] == 'word') {
 
         if (!$proto->isReadOnlyCommand($struct)) {
           $this->didSeeWrite = true;
           $this->requireWriteAccess($struct[0]['value']);
         }
 
         // Several other commands also pass in URLs. We need to translate
         // all of these into the internal representation; this also makes sure
         // they're valid and accessible.
 
         switch ($struct[0]['value']) {
           case 'reparent':
             // ( reparent ( url ) )
             $struct[1]['value'][0]['value'] = $this->makeInternalURI(
               $struct[1]['value'][0]['value']);
             $message_raw = $proto->serializeStruct($struct);
             break;
           case 'switch':
             // ( switch ( ( rev ) target recurse url ... ) )
             $struct[1]['value'][3]['value'] = $this->makeInternalURI(
               $struct[1]['value'][3]['value']);
             $message_raw = $proto->serializeStruct($struct);
             break;
           case 'diff':
             // ( diff ( ( rev ) target recurse ignore-ancestry url ... ) )
             $struct[1]['value'][4]['value'] = $this->makeInternalURI(
               $struct[1]['value'][4]['value']);
             $message_raw = $proto->serializeStruct($struct);
             break;
           case 'add-file':
           case 'add-dir':
             // ( add-file ( path dir-token file-token [ copy-path copy-rev ] ) )
             // ( add-dir ( path parent child [ copy-path copy-rev ] ) )
             if (isset($struct[1]['value'][3]['value'][0]['value'])) {
               $copy_from = $struct[1]['value'][3]['value'][0]['value'];
               $copy_from = $this->makeInternalURI($copy_from);
               $struct[1]['value'][3]['value'][0]['value'] = $copy_from;
             }
             $message_raw = $proto->serializeStruct($struct);
             break;
         }
       }
 
       $result[] = $message_raw;
     }
 
     if (!$result) {
       return null;
     }
 
     return implode('', $result);
   }
 
   public function willReadMessageCallback(
     PhabricatorSSHPassthruCommand $command,
     $message) {
 
     $proto = $this->outProtocol;
     $messages = $proto->writeData($message);
 
     $result = array();
     foreach ($messages as $message) {
       $message_raw = $message['raw'];
       $struct = $message['structure'];
 
       if (isset($struct[0]) && ($struct[0]['type'] == 'word')) {
 
         if ($struct[0]['value'] == 'success') {
           switch ($this->outPhaseCount) {
             case 0:
               // This is the "greeting", which announces capabilities.
 
               // We already sent this when we were figuring out which
               // repository this request is for, so we aren't going to send
               // it again.
 
               // Instead, we're going to replay the client's response (which
               // we also already read).
 
               $command = $this->getCommand();
               $command->writeIORead($this->peekBuffer);
               $command->setPauseIOReads(false);
 
               $message_raw = null;
               break;
             case 1:
               // This responds to the client greeting, and announces auth.
               break;
             case 2:
               // This responds to auth, which should be trivial over SSH.
               break;
             case 3:
               // This contains the URI of the repository. We need to edit it;
               // if it does not match what the client requested it will reject
               // the response.
               $struct[1]['value'][1]['value'] = $this->makeExternalURI(
                 $struct[1]['value'][1]['value']);
               $message_raw = $proto->serializeStruct($struct);
               break;
             default:
               // We don't care about other protocol frames.
               break;
           }
 
           $this->outPhaseCount++;
         } else if ($struct[0]['value'] == 'failure') {
           // Find any error messages which include the internal URI, and
           // replace the text with the external URI.
           foreach ($struct[1]['value'] as $key => $error) {
             $code = $error['value'][0]['value'];
             $message = $error['value'][1]['value'];
 
             $message = str_replace(
               $this->internalBaseURI,
               $this->externalBaseURI,
               $message);
 
             // Derp derp derp derp derp. The structure looks like this:
             //   ( failure ( ( code message ... ) ... ) )
             $struct[1]['value'][$key]['value'][1]['value'] = $message;
           }
           $message_raw = $proto->serializeStruct($struct);
         }
 
       }
 
       if ($message_raw !== null) {
         $result[] = $message_raw;
       }
     }
 
     if (!$result) {
       return null;
     }
 
     return implode('', $result);
   }
 
   private function getPathFromSubversionURI($uri_string) {
     $uri = new PhutilURI($uri_string);
 
     $proto = $uri->getProtocol();
     if ($proto !== 'svn+ssh') {
       throw new Exception(
         pht(
           'Protocol for URI "%s" MUST be "%s".',
           $uri_string,
           'svn+ssh'));
     }
     $path = $uri->getPath();
 
     // Subversion presumably deals with this, but make sure there's nothing
     // sketchy going on with the URI.
     if (preg_match('(/\\.\\./)', $path)) {
       throw new Exception(
         pht(
           'String "%s" is invalid in path specification "%s".',
           '/../',
           $uri_string));
     }
 
     $path = $this->normalizeSVNPath($path);
 
     return $path;
   }
 
   private function makeInternalURI($uri_string) {
     if ($this->isProxying) {
       return $uri_string;
     }
 
     $uri = new PhutilURI($uri_string);
 
     $repository = $this->getRepository();
 
     $path = $this->getPathFromSubversionURI($uri_string);
     $external_base = $this->getBaseRequestPath();
 
     // Replace "/diffusion/X" in the request with the repository local path,
     // so "/diffusion/X/master/" becomes "/path/to/repository/X/master/".
     $local_path = rtrim($repository->getLocalPath(), '/');
     $path = $local_path.substr($path, strlen($external_base));
 
     // NOTE: We are intentionally NOT removing username information from the
     // URI. Subversion retains it over the course of the request and considers
     // two repositories with different username identifiers to be distinct and
     // incompatible.
 
     $uri->setPath($path);
 
     // If this is happening during the handshake, these are the base URIs for
     // the request.
     if ($this->externalBaseURI === null) {
       $pre = (string)id(clone $uri)->setPath('');
 
       $external_path = $external_base;
       $external_path = $this->normalizeSVNPath($external_path);
       $this->externalBaseURI = $pre.$external_path;
 
       $internal_path = rtrim($repository->getLocalPath(), '/');
       $internal_path = $this->normalizeSVNPath($internal_path);
       $this->internalBaseURI = $pre.$internal_path;
     }
 
     return (string)$uri;
   }
 
   private function makeExternalURI($uri) {
     if ($this->isProxying) {
       return $uri;
     }
 
     $internal = $this->internalBaseURI;
     $external = $this->externalBaseURI;
 
     if (strncmp($uri, $internal, strlen($internal)) === 0) {
       $uri = $external.substr($uri, strlen($internal));
     }
 
     return $uri;
   }
 
   private function normalizeSVNPath($path) {
     // Subversion normalizes redundant slashes internally, so normalize them
     // here as well to make sure things match up.
     $path = preg_replace('(/+)', '/', $path);
 
     return $path;
   }
 
+  protected function raiseWrongVCSException(
+    PhabricatorRepository $repository) {
+    throw new Exception(
+      pht(
+        'This repository ("%s") is not a Subversion repository. Use "%s" to '.
+        'interact with this repository.',
+        $repository->getDisplayName(),
+        $repository->getVersionControlSystem()));
+  }
+
 }