diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -662,6 +662,7 @@
     'DiffusionGitResponse' => 'applications/diffusion/response/DiffusionGitResponse.php',
     'DiffusionGitSSHWorkflow' => 'applications/diffusion/ssh/DiffusionGitSSHWorkflow.php',
     'DiffusionGitUploadPackSSHWorkflow' => 'applications/diffusion/ssh/DiffusionGitUploadPackSSHWorkflow.php',
+    'DiffusionGitWireProtocol' => 'applications/diffusion/protocol/DiffusionGitWireProtocol.php',
     'DiffusionHistoryController' => 'applications/diffusion/controller/DiffusionHistoryController.php',
     'DiffusionHistoryQueryConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionHistoryQueryConduitAPIMethod.php',
     'DiffusionHistoryTableView' => 'applications/diffusion/view/DiffusionHistoryTableView.php',
@@ -4906,6 +4907,7 @@
       'DiffusionRepositoryClusterEngineLogInterface',
     ),
     'DiffusionGitUploadPackSSHWorkflow' => 'DiffusionGitSSHWorkflow',
+    'DiffusionGitWireProtocol' => 'Phobject',
     'DiffusionHistoryController' => 'DiffusionController',
     'DiffusionHistoryQueryConduitAPIMethod' => 'DiffusionQueryConduitAPIMethod',
     'DiffusionHistoryTableView' => 'DiffusionView',
diff --git a/src/applications/diffusion/protocol/DiffusionGitWireProtocol.php b/src/applications/diffusion/protocol/DiffusionGitWireProtocol.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/protocol/DiffusionGitWireProtocol.php
@@ -0,0 +1,176 @@
+<?php
+
+final class DiffusionGitWireProtocol extends Phobject {
+
+  private $buffer = '';
+  private $state = 'head';
+  private $expectBytes;
+  private $expectPacks;
+
+  private $packType;
+  private $packSize;
+  private $packShift;
+
+  public function writeData($data) {
+    $this->buffer .= $data;
+
+    while (true) {
+      if ($this->state == 'head') {
+        if (strlen($this->buffer) < 4) {
+          break;
+        }
+
+        $head = substr($this->buffer, 0, 4);
+        $this->buffer = substr($this->buffer, 4);
+
+        if ($head == 'PACK') {
+          $this->state = 'pack-version';
+          continue;
+        }
+
+        if (!preg_match('/^[a-f0-9]{4}\z/', $head)) {
+          throw new Exception(
+            pht(
+              'Expected Git wire protocol frame length header (four hex '.
+              'characters, like "02af") but got "%s".',
+              $head));
+        }
+
+        $bytes = hexdec($head);
+
+        // NOTE: This header is documented as containing the length of the
+        // "rest of the line", but in practice it appears to include its own
+        // length.
+        if ($bytes >= 4) {
+          $this->expectBytes = ($bytes - 4);
+        } else if (!$bytes) {
+          $this->expectBytes = $bytes;
+        } else {
+          throw new Exception(
+            pht(
+              'Expected Git wire protocol frame length header with valid '.
+              'value (0, or >= 4 bytes) but got invalid value ("%s").',
+              $bytes));
+        }
+
+        $this->state = 'body';
+      } else if ($this->state == 'body') {
+        if (strlen($this->buffer) < $this->expectBytes) {
+          break;
+        }
+
+        $body = substr($this->buffer, 0, $this->expectBytes);
+        $this->buffer = substr($this->buffer, $this->expectBytes);
+
+        $this->state = 'head';
+      } else if ($this->state == 'pack-version') {
+        if (strlen($this->buffer) < 4) {
+          break;
+        }
+
+        $version = substr($this->buffer, 0, 4);
+        $this->buffer = substr($this->buffer, 4);
+
+        $expect = "\x00\x00\x00\x02";
+        if ($version !== $expect) {
+          throw new Exception(
+            pht(
+              'Expected Git wire protocol packfile version 2 (four binary '.
+              'bytes, "%s") but got "%s".',
+              bin2hex($expect),
+              bin2hex($version)));
+        }
+
+        $this->state = 'pack-length';
+      } else if ($this->state == 'pack-length') {
+        if (strlen($this->buffer) < 4) {
+          break;
+        }
+
+        $length = substr($this->buffer, 0, 4);
+        $this->buffer = substr($this->buffer, 4);
+
+        $value = head(unpack('N', $length));
+        if (!$value) {
+          throw new Exception(
+            pht(
+              'Expected Git wire protocol pack count (four binary '.
+              'bytes) but got "%s".',
+              bin2hex($length)));
+        }
+
+        $this->expectPacks = $value;
+        $this->state = 'pack-head';
+      } else if ($this->state == 'pack-head') {
+        if (!$this->expectPacks) {
+          $this->state = 'pack-tail';
+          continue;
+        }
+
+        if (!strlen($this->buffer)) {
+          break;
+        }
+
+        $this->expectPacks--;
+
+        $byte = substr($this->buffer, 0, 1);
+        $this->buffer = substr($this->buffer, 1);
+
+        $byte = ord($byte);
+        $this->packType = ($byte >> 4) & 7;
+        $this->packSize = ($byte & 15);
+        $this->packShift = 4;
+
+        if ($byte & 0x80) {
+          $this->state = 'pack-head-more';
+        } else {
+          $this->state = 'pack-body';
+        }
+      } else if ($this->state == 'pack-head-more') {
+        if (!strlen($this->buffer)) {
+          break;
+        }
+
+        $byte = substr($this->buffer, 0, 1);
+        $this->buffer = substr($this->buffer, 1);
+
+        $byte = ord($byte);
+
+        $this->packSize += ($byte & 0x7F) << $this->packShift;
+        $this->packShift += 7;
+
+        if ($byte & 0x80) {
+          $this->state = 'pack-head-more';
+        } else {
+          $this->state = 'pack-body';
+        }
+      } else if ($this->state == 'pack-body') {
+        $available = strlen($this->buffer);
+        $expect = $this->packSize;
+
+        $read_bytes = min($available, $expect);
+        if ($read_bytes) {
+          $pack_data = substr($this->buffer, 0, $read_bytes);
+          $this->buffer = substr($this->buffer, $read_bytes);
+          $this->packSize -= $read_bytes;
+        }
+
+        if (!$this->expectBytes) {
+          $this->state = 'pack-head';
+        }
+      } else if ($this->state == 'pack-tail') {
+        if (strlen($this->buffer) < 20) {
+          break;
+        }
+
+        $sha1 = substr($this->buffer, 0, 20);
+        $this->buffer = substr($this->buffer, 20);
+
+        $this->state = 'head';
+      }
+    }
+
+    return $data;
+  }
+
+}
diff --git a/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php
--- a/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php
@@ -2,6 +2,9 @@
 
 final class DiffusionGitReceivePackSSHWorkflow extends DiffusionGitSSHWorkflow {
 
+  private $inProtocol;
+  private $outProtocol;
+
   protected function didConstruct() {
     $this->setName('git-receive-pack');
     $this->setArguments(
@@ -28,6 +31,7 @@
 
     if ($this->shouldProxy()) {
       $command = $this->getProxyCommand();
+      $intercept = false;
       $did_synchronize = false;
 
       if ($device) {
@@ -38,6 +42,7 @@
       }
     } else {
       $command = csprintf('git-receive-pack %s', $repository->getLocalPath());
+      $intercept = true;
       $did_synchronize = true;
       $cluster_engine->synchronizeWorkingCopyBeforeWrite();
 
@@ -51,7 +56,7 @@
 
     $caught = null;
     try {
-      $err = $this->executeRepositoryCommand($command);
+      $err = $this->executeRepositoryCommand($command, $intercept);
     } catch (Exception $ex) {
       $caught = $ex;
     }
@@ -76,17 +81,51 @@
     return $err;
   }
 
-  private function executeRepositoryCommand($command) {
+  private function executeRepositoryCommand($command, $intercept) {
     $repository = $this->getRepository();
     $command = PhabricatorDaemon::sudoCommandAsDaemonUser($command);
 
     $future = id(new ExecFuture('%C', $command))
       ->setEnv($this->getEnvironment());
 
-    return $this->newPassthruCommand()
+    $command = $this->newPassthruCommand()
       ->setIOChannel($this->getIOChannel())
-      ->setCommandChannelFromExecFuture($future)
-      ->execute();
+      ->setCommandChannelFromExecFuture($future);
+
+    if ($intercept) {
+      $this->inProtocol = new DiffusionGitWireProtocol();
+      $this->outProtocol = new DiffusionGitWireProtocol();
+
+      $command
+        ->setWillReadCallback(array($this, 'willReadMessageCallback'))
+        ->setWillWriteCallback(array($this, 'willWriteMessageCallback'));
+    }
+
+    return $command->execute();
+  }
+
+  public function willReadMessageCallback(
+    PhabricatorSSHPassthruCommand $command,
+    $message) {
+
+    $f = fopen('/tmp/git-response.log', 'a');
+    fwrite($f, $message);
+    fflush($f);
+    fclose($f);
+
+    return $this->outProtocol->writeData($message);
+  }
+
+  public function willWriteMessageCallback(
+    PhabricatorSSHPassthruCommand $command,
+    $message) {
+
+    $f = fopen('/tmp/git-request.log', 'a');
+    fwrite($f, $message);
+    fflush($f);
+    fclose($f);
+
+    return $this->inProtocol->writeData($message);
   }
 
 }