diff --git a/scripts/repository/commit_hook.php b/scripts/repository/commit_hook.php
index 86e927f41a..25afb714e5 100755
--- a/scripts/repository/commit_hook.php
+++ b/scripts/repository/commit_hook.php
@@ -29,11 +29,16 @@ $engine->setRepository($repository);
 
 // Figure out which user is writing the commit.
 
-if ($repository->isGit()) {
+if ($repository->isGit() || $repository->isHg()) {
   $username = getenv('PHABRICATOR_USER');
   if (!strlen($username)) {
     throw new Exception(pht('usage: PHABRICATOR_USER should be defined!'));
   }
+
+  // TODO: If this is a Mercurial repository, the hook we're responding to
+  // is available in $argv[2]. It's unclear if we actually need this, or if
+  // we can block all actions we care about with just pretxnchangegroup.
+
 } else if ($repository->isSVN()) {
   // NOTE: In Subversion, the entire environment gets wiped so we can't read
   // PHABRICATOR_USER. Instead, we've set "--tunnel-user" to specify the
@@ -50,7 +55,7 @@ if ($repository->isGit()) {
 
   $engine->setSubversionTransactionInfo($svn_txn, $svn_repo);
 } else {
-  throw new Exceptiont(pht('Unknown repository type.'));
+  throw new Exception(pht('Unknown repository type.'));
 }
 
 $user = id(new PhabricatorPeopleQuery())
@@ -67,9 +72,16 @@ $engine->setViewer($user);
 
 // Read stdin for the hook engine.
 
-$stdin = @file_get_contents('php://stdin');
-if ($stdin === false) {
-  throw new Exception(pht('Failed to read stdin!'));
+if ($repository->isHg()) {
+  // Mercurial leaves stdin open, so we can't just read it until EOF.
+  $stdin = '';
+} else {
+  // Git and Subversion write data into stdin and then close it. Read the
+  // data.
+  $stdin = @file_get_contents('php://stdin');
+  if ($stdin === false) {
+    throw new Exception(pht('Failed to read stdin!'));
+  }
 }
 
 $engine->setStdin($stdin);
diff --git a/src/applications/diffusion/controller/DiffusionServeController.php b/src/applications/diffusion/controller/DiffusionServeController.php
index de7c2e1eb2..6d72184216 100644
--- a/src/applications/diffusion/controller/DiffusionServeController.php
+++ b/src/applications/diffusion/controller/DiffusionServeController.php
@@ -406,7 +406,9 @@ final class DiffusionServeController extends DiffusionController {
     return $user;
   }
 
-  private function serveMercurialRequest(PhabricatorRepository $repository) {
+  private function serveMercurialRequest(
+    PhabricatorRepository $repository,
+    PhabricatorUser $viewer) {
     $request = $this->getRequest();
 
     $bin = Filesystem::resolveBinary('hg');
@@ -414,7 +416,9 @@ final class DiffusionServeController extends DiffusionController {
       throw new Exception("Unable to find `hg` in PATH!");
     }
 
-    $env = array();
+    $env = array(
+      'PHABRICATOR_USER' => $viewer->getUsername(),
+    );
     $input = PhabricatorStartup::getRawInput();
 
     $cmd = $request->getStr('cmd');
diff --git a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
index 282ae16697..7a6855de46 100644
--- a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
+++ b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
@@ -51,6 +51,9 @@ final class DiffusionCommitHookEngine extends Phobject {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         $err = $this->executeSubversionHook();
         break;
+      case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
+        $err = $this->executeMercurialHook();
+        break;
       default:
         throw new Exception(pht('Unsupported repository type "%s"!', $type));
     }
@@ -73,6 +76,13 @@ final class DiffusionCommitHookEngine extends Phobject {
     return 0;
   }
 
+  private function executeMercurialHook() {
+
+    // TODO: Here, too, useful things should be done.
+
+    return 0;
+  }
+
   private function parseGitUpdates($stdin) {
     $updates = array();
 
diff --git a/src/applications/diffusion/ssh/DiffusionSSHMercurialServeWorkflow.php b/src/applications/diffusion/ssh/DiffusionSSHMercurialServeWorkflow.php
index 46eee57610..e7697e6083 100644
--- a/src/applications/diffusion/ssh/DiffusionSSHMercurialServeWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionSSHMercurialServeWorkflow.php
@@ -42,7 +42,8 @@ final class DiffusionSSHMercurialServeWorkflow
     $command = csprintf('hg -R %s serve --stdio', $repository->getLocalPath());
     $command = PhabricatorDaemon::sudoCommandAsDaemonUser($command);
 
-    $future = new ExecFuture('%C', $command);
+    $future = id(new ExecFuture('%C', $command))
+      ->setEnv($this->getEnvironment());
 
     $io_channel = $this->getIOChannel();
     $protocol_channel = new DiffusionSSHMercurialWireClientProtocolChannel(
diff --git a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
index ab3c759fae..c7e8e0ae7e 100644
--- a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
+++ b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
@@ -87,6 +87,8 @@ final class PhabricatorRepositoryPullEngine
             $this->installGitHook();
           } else if ($is_svn) {
             $this->installSubversionHook();
+          } else if ($is_hg) {
+            $this->installMercurialHook();
           } else {
             $this->logPull(
               pht(
@@ -335,7 +337,7 @@ final class PhabricatorRepositoryPullEngine
         $path);
     } else {
       $repository->execxRemoteCommand(
-        'clone -- %s %s',
+        'clone --noupdate -- %s %s',
         $repository->getRemoteURI(),
         $path);
     }
@@ -383,6 +385,33 @@ final class PhabricatorRepositoryPullEngine
   }
 
 
+  /**
+   * @task hg
+   */
+  private function installMercurialHook() {
+    $repository = $this->getRepository();
+    $path = $repository->getLocalPath().'.hg/hgrc';
+
+    $root = dirname(phutil_get_library_root('phabricator'));
+    $bin = $root.'/bin/commit-hook';
+
+    $data = array();
+    $data[] = '[hooks]';
+    $data[] = csprintf(
+      'pretxnchangegroup.phabricator = %s %s %s',
+      $bin,
+      $repository->getCallsign(),
+      'pretxnchangegroup');
+    $data[] = null;
+
+    $data = implode("\n", $data);
+
+    $this->log('%s', pht('Installing commit hook config to "%s"...', $path));
+
+    Filesystem::writeFile($path, $data);
+  }
+
+
 /* -(  Pulling Subversion Working Copies  )---------------------------------- */