Record more details about where a write is taking place while holding a cluster lock

Summary: Ref T4292. This will let the UI and future `bin/repository` tools give administrators more tools to understand problems when reporting or resolving them.

Test Plan:
  - Pushed fully clean repository.
  - Pushed previously-pushed repository.
  - Forced write to abort, inspected useful information in the database.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4292

Differential Revision: https://secure.phabricator.com/D15748

resources/sql/autopatches/20160418.repoversion.1.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_repository.repository_workingcopyversion
+  ADD writeProperties LONGTEXT COLLATE {$COLLATE_TEXT};

src/applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php

@@ -26,7 +26,8 @@ final class DiffusionGitReceivePackSSHWorkflow extends DiffusionGitSSHWorkflow {
       $command = csprintf('git-receive-pack %s', $repository->getLocalPath());
 
       $did_synchronize = true;
-      $repository->synchronizeWorkingCopyBeforeWrite();
+      $viewer = $this->getUser();
+      $repository->synchronizeWorkingCopyBeforeWrite($viewer);
     }
 
     $caught = null;

src/applications/repository/storage/PhabricatorRepository.php

@@ -2482,7 +2482,8 @@ final class PhabricatorRepository extends PhabricatorRepositoryDAO
   /**
    * @task sync
    */
-  public function synchronizeWorkingCopyBeforeWrite() {
+  public function synchronizeWorkingCopyBeforeWrite(
+    PhabricatorUser $actor) {
     if (!$this->shouldEnableSynchronization()) {
       return;
     }
@@ -2516,7 +2517,12 @@ final class PhabricatorRepository extends PhabricatorRepositoryDAO
 
     PhabricatorRepositoryWorkingCopyVersion::willWrite(
       $repository_phid,
-      $device_phid);
+      $device_phid,
+      array(
+        'userPHID' => $actor->getPHID(),
+        'epoch' => PhabricatorTime::getNow(),
+        'devicePHID' => $device_phid,
+      ));
 
     $this->clusterWriteVersion = $max_version;
     $this->clusterWriteLock = $write_lock;

src/applications/repository/storage/PhabricatorRepositoryWorkingCopyVersion.php

@@ -7,6 +7,7 @@ final class PhabricatorRepositoryWorkingCopyVersion
   protected $devicePHID;
   protected $repositoryVersion;
   protected $isWriting;
+  protected $writeProperties;
 
   protected function getConfiguration() {
     return array(
@@ -14,6 +15,7 @@ final class PhabricatorRepositoryWorkingCopyVersion
       self::CONFIG_COLUMN_SCHEMA => array(
         'repositoryVersion' => 'uint32',
         'isWriting' => 'bool',
+        'writeProperties' => 'text?',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_workingcopy' => array(
@@ -66,7 +68,10 @@ final class PhabricatorRepositoryWorkingCopyVersion
    * lock is released by default. This is a durable lock which stays locked
    * by default.
    */
-  public static function willWrite($repository_phid, $device_phid) {
+  public static function willWrite(
+    $repository_phid,
+    $device_phid,
+    array $write_properties) {
     $version = new self();
     $conn_w = $version->establishConnection('w');
     $table = $version->getTableName();
@@ -74,16 +79,19 @@ final class PhabricatorRepositoryWorkingCopyVersion
     queryfx(
       $conn_w,
       'INSERT INTO %T
-        (repositoryPHID, devicePHID, repositoryVersion, isWriting)
+        (repositoryPHID, devicePHID, repositoryVersion, isWriting,
+          writeProperties)
         VALUES
-        (%s, %s, %d, %d)
+        (%s, %s, %d, %d, %s)
         ON DUPLICATE KEY UPDATE
-          isWriting = VALUES(isWriting)',
+          isWriting = VALUES(isWriting),
+          writeProperties = VALUES(writeProperties)',
       $table,
       $repository_phid,
       $device_phid,
       0,
-      1);
+      1,
+      phutil_json_encode($write_properties));
   }
 
 
@@ -101,7 +109,10 @@ final class PhabricatorRepositoryWorkingCopyVersion
 
     queryfx(
       $conn_w,
-      'UPDATE %T SET repositoryVersion = %d, isWriting = 0
+      'UPDATE %T SET
+          repositoryVersion = %d,
+          isWriting = 0,
+          writeProperties = null
         WHERE
           repositoryPHID = %s AND
           devicePHID = %s AND