diff --git a/scripts/repository/commit_hook.php b/scripts/repository/commit_hook.php
index 56e828ab7a..4f6997c52a 100755
--- a/scripts/repository/commit_hook.php
+++ b/scripts/repository/commit_hook.php
@@ -32,14 +32,14 @@ $root = dirname(dirname(dirname(__FILE__)));
 require_once $root.'/scripts/__init_script__.php';
 
 if ($argc < 2) {
-  throw new Exception(pht('usage: commit-hook <callsign>'));
+  throw new Exception(pht('usage: commit-hook <repository>'));
 }
 
 $engine = new DiffusionCommitHookEngine();
 
 $repository = id(new PhabricatorRepositoryQuery())
   ->setViewer(PhabricatorUser::getOmnipotentUser())
-  ->withCallsigns(array($argv[1]))
+  ->withIdentifiers(array($argv[1]))
   ->needProjectPHIDs(true)
   ->executeOne();
 
@@ -62,8 +62,9 @@ if ($repository->isGit() || $repository->isHg()) {
   if (!strlen($username)) {
     throw new Exception(
       pht(
-        'Usage: %s should be defined!',
-        DiffusionCommitHookEngine::ENV_USER));
+        'No Direct Pushes: You are pushing directly to a repository hosted '.
+        'by Phabricator. This will not work. See "No Direct Pushes" in the '.
+        'documentation for more information.'));
   }
 
   if ($repository->isHg()) {
@@ -77,7 +78,7 @@ if ($repository->isGit() || $repository->isHg()) {
   // specify the correct user; read this user out of the commit log.
 
   if ($argc < 4) {
-    throw new Exception(pht('usage: commit-hook <callsign> <repo> <txn>'));
+    throw new Exception(pht('usage: commit-hook <repository> <repo> <txn>'));
   }
 
   $svn_repo = $argv[2];
diff --git a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
index 30ab234027..690f9425a4 100644
--- a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
+++ b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
@@ -192,7 +192,7 @@ final class PhabricatorRepositoryPullEngine
   }
 
   private function getHookContextIdentifier(PhabricatorRepository $repository) {
-    $identifier = $repository->getCallsign();
+    $identifier = $repository->getPHID();
 
     $instance = PhabricatorEnv::getEnvConfig('cluster.instance');
     if (strlen($instance)) {
diff --git a/src/docs/user/userguide/diffusion_hosting.diviner b/src/docs/user/userguide/diffusion_hosting.diviner
index 6427be92e5..f4baddf5a5 100644
--- a/src/docs/user/userguide/diffusion_hosting.diviner
+++ b/src/docs/user/userguide/diffusion_hosting.diviner
@@ -371,6 +371,41 @@ with `sudoers` configuration.
     is caused by SVN wiping the environment (including PATH) when invoking
     commit hooks.
 
+No Direct Pushes
+================
+
+You may get an error about "No Direct Pushes" when trying to push. This means
+you are pushing directly to the repository instead of pushing through
+Phabricator. This is not supported: writes to hosted repositories must go
+through Phabricator so it can perform authentication, enforce permissions,
+write logs, proxy requests, apply rewriting, etc.
+
+One way to do a direct push by mistake is to use a `file:///` URI to interact
+with the repository from the same machine. This is not supported. Instead, use
+one of the repository URIs provided in the web interface, even if you're
+working on the same machine.
+
+Another way to do a direct push is to misconfigure SSH (or not configure it at
+all) so that none of the logic described above runs and you just connect
+normally as a system user. In this case, the `ssh` test described above will
+fail (you'll get a command prompt when you connect, instead of the message you
+are supposed to get, as described above).
+
+If you encounter this error: make sure you're using a remote URI given to
+you by Diffusion in the web interface, then run through the troubleshooting
+steps above carefully.
+
+Sometimes users encounter this problem because they skip this whole document
+assuming they don't need to configure anything. This will not work, and you
+MUST configure things as described above for hosted repositories to work.
+
+The technical reason this error occurs is that the `PHABRICATOR_USER` variable
+is not defined in the environment when commit hooks run. This variable is set
+by Phabricator when a request passes through the authentication layer that this
+document provides instructions for configuring. Its absence indicates that the
+request did not pass through Phabricator.
+
+
 = Next Steps =
 
 Once hosted repositories are set up: