diff --git a/resources/sql/autopatches/20180430.repo_identity.sql b/resources/sql/autopatches/20180430.repo_identity.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20180430.repo_identity.sql
@@ -0,0 +1,14 @@
+CREATE TABLE {$NAMESPACE}_repository.repository_identity (
+  id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  phid VARBINARY(64) NOT NULL,
+  dateCreated INT UNSIGNED NOT NULL,
+  dateModified INT UNSIGNED NOT NULL,
+  automaticGuessedUserPHID VARBINARY(64) DEFAULT NULL,
+  manuallySetUserPHID VARBINARY(64) DEFAULT NULL,
+  currentEffectiveUserPHID VARBINARY(64) DEFAULT NULL,
+  identityNameHash BINARY(12) NOT NULL,
+  identityNameRaw LONGBLOB NOT NULL,
+  identityNameEncoding VARCHAR(16) DEFAULT NULL COLLATE {$COLLATE_TEXT},
+  UNIQUE KEY `key_phid` (phid),
+  UNIQUE KEY `key_identity` (identityNameHash)
+) ENGINE=InnoDB DEFAULT CHARSET={$CHARSET} COLLATE={$COLLATE_TEXT};
diff --git a/resources/sql/autopatches/20180504.repo_identity.author.sql b/resources/sql/autopatches/20180504.repo_identity.author.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20180504.repo_identity.author.sql
@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_repository.repository_identity
+  ADD COLUMN authorPHID VARBINARY(64) NOT NULL;
diff --git a/resources/sql/autopatches/20180504.repo_identity.xaction.sql b/resources/sql/autopatches/20180504.repo_identity.xaction.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20180504.repo_identity.xaction.sql
@@ -0,0 +1,19 @@
+CREATE TABLE {$NAMESPACE}_repository.repository_identitytransaction (
+  id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  phid VARBINARY(64) NOT NULL,
+  authorPHID VARBINARY(64) NOT NULL,
+  objectPHID VARBINARY(64) NOT NULL,
+  viewPolicy VARBINARY(64) NOT NULL,
+  editPolicy VARBINARY(64) NOT NULL,
+  commentPHID VARBINARY(64) DEFAULT NULL,
+  commentVersion INT UNSIGNED NOT NULL,
+  transactionType VARCHAR(32) NOT NULL,
+  oldValue LONGTEXT NOT NULL,
+  newValue LONGTEXT NOT NULL,
+  contentSource LONGTEXT NOT NULL,
+  metadata LONGTEXT NOT NULL,
+  dateCreated INT UNSIGNED NOT NULL,
+  dateModified INT UNSIGNED NOT NULL,
+  UNIQUE KEY `key_phid` (`phid`),
+  KEY `key_object` (`objectPHID`)
+) ENGINE=InnoDB DEFAULT CHARSET={$CHARSET} COLLATE {$COLLATE_TEXT};
diff --git a/resources/sql/autopatches/20180509.repo_identity.commits.sql b/resources/sql/autopatches/20180509.repo_identity.commits.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20180509.repo_identity.commits.sql
@@ -0,0 +1,3 @@
+ALTER TABLE {$NAMESPACE}_repository.repository_commit
+  ADD COLUMN authorIdentityPHID VARBINARY(64) DEFAULT NULL,
+  ADD COLUMN committerIdentityPHID VARBINARY(64) DEFAULT NULL;
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
@@ -814,6 +814,13 @@
     'DiffusionHistoryTableView' => 'applications/diffusion/view/DiffusionHistoryTableView.php',
     'DiffusionHistoryView' => 'applications/diffusion/view/DiffusionHistoryView.php',
     'DiffusionHovercardEngineExtension' => 'applications/diffusion/engineextension/DiffusionHovercardEngineExtension.php',
+    'DiffusionIdentityAssigneeDatasource' => 'applications/diffusion/typeahead/DiffusionIdentityAssigneeDatasource.php',
+    'DiffusionIdentityAssigneeEditField' => 'applications/diffusion/editfield/DiffusionIdentityAssigneeEditField.php',
+    'DiffusionIdentityAssigneeSearchField' => 'applications/diffusion/searchfield/DiffusionIdentityAssigneeSearchField.php',
+    'DiffusionIdentityEditController' => 'applications/diffusion/controller/DiffusionIdentityEditController.php',
+    'DiffusionIdentityListController' => 'applications/diffusion/controller/DiffusionIdentityListController.php',
+    'DiffusionIdentityUnassignedDatasource' => 'applications/diffusion/typeahead/DiffusionIdentityUnassignedDatasource.php',
+    'DiffusionIdentityViewController' => 'applications/diffusion/controller/DiffusionIdentityViewController.php',
     'DiffusionInlineCommentController' => 'applications/diffusion/controller/DiffusionInlineCommentController.php',
     'DiffusionInlineCommentPreviewController' => 'applications/diffusion/controller/DiffusionInlineCommentPreviewController.php',
     'DiffusionInternalGitRawDiffQueryConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionInternalGitRawDiffQueryConduitAPIMethod.php',
@@ -935,6 +942,8 @@
     'DiffusionRepositoryEditUpdateController' => 'applications/diffusion/controller/DiffusionRepositoryEditUpdateController.php',
     'DiffusionRepositoryFunctionDatasource' => 'applications/diffusion/typeahead/DiffusionRepositoryFunctionDatasource.php',
     'DiffusionRepositoryHistoryManagementPanel' => 'applications/diffusion/management/DiffusionRepositoryHistoryManagementPanel.php',
+    'DiffusionRepositoryIdentityEditor' => 'applications/diffusion/editor/DiffusionRepositoryIdentityEditor.php',
+    'DiffusionRepositoryIdentitySearchEngine' => 'applications/diffusion/query/DiffusionRepositoryIdentitySearchEngine.php',
     'DiffusionRepositoryListController' => 'applications/diffusion/controller/DiffusionRepositoryListController.php',
     'DiffusionRepositoryManageController' => 'applications/diffusion/controller/DiffusionRepositoryManageController.php',
     'DiffusionRepositoryManagePanelsController' => 'applications/diffusion/controller/DiffusionRepositoryManagePanelsController.php',
@@ -4078,6 +4087,16 @@
     'PhabricatorRepositoryGitLFSRefQuery' => 'applications/repository/query/PhabricatorRepositoryGitLFSRefQuery.php',
     'PhabricatorRepositoryGraphCache' => 'applications/repository/graphcache/PhabricatorRepositoryGraphCache.php',
     'PhabricatorRepositoryGraphStream' => 'applications/repository/daemon/PhabricatorRepositoryGraphStream.php',
+    'PhabricatorRepositoryIdentity' => 'applications/repository/storage/PhabricatorRepositoryIdentity.php',
+    'PhabricatorRepositoryIdentityAssignTransaction' => 'applications/repository/xaction/PhabricatorRepositoryIdentityAssignTransaction.php',
+    'PhabricatorRepositoryIdentityChangeWorker' => 'applications/repository/worker/PhabricatorRepositoryIdentityChangeWorker.php',
+    'PhabricatorRepositoryIdentityEditEngine' => 'applications/repository/engine/PhabricatorRepositoryIdentityEditEngine.php',
+    'PhabricatorRepositoryIdentityFerretEngine' => 'applications/repository/search/PhabricatorRepositoryIdentityFerretEngine.php',
+    'PhabricatorRepositoryIdentityPHIDType' => 'applications/repository/phid/PhabricatorRepositoryIdentityPHIDType.php',
+    'PhabricatorRepositoryIdentityQuery' => 'applications/repository/query/PhabricatorRepositoryIdentityQuery.php',
+    'PhabricatorRepositoryIdentityTransaction' => 'applications/repository/storage/PhabricatorRepositoryIdentityTransaction.php',
+    'PhabricatorRepositoryIdentityTransactionQuery' => 'applications/repository/query/PhabricatorRepositoryIdentityTransactionQuery.php',
+    'PhabricatorRepositoryIdentityTransactionType' => 'applications/repository/xaction/PhabricatorRepositoryIdentityTransactionType.php',
     'PhabricatorRepositoryManagementCacheWorkflow' => 'applications/repository/management/PhabricatorRepositoryManagementCacheWorkflow.php',
     'PhabricatorRepositoryManagementClusterizeWorkflow' => 'applications/repository/management/PhabricatorRepositoryManagementClusterizeWorkflow.php',
     'PhabricatorRepositoryManagementDiscoverWorkflow' => 'applications/repository/management/PhabricatorRepositoryManagementDiscoverWorkflow.php',
@@ -6144,6 +6163,13 @@
     'DiffusionHistoryTableView' => 'DiffusionHistoryView',
     'DiffusionHistoryView' => 'DiffusionView',
     'DiffusionHovercardEngineExtension' => 'PhabricatorHovercardEngineExtension',
+    'DiffusionIdentityAssigneeDatasource' => 'PhabricatorTypeaheadCompositeDatasource',
+    'DiffusionIdentityAssigneeEditField' => 'PhabricatorTokenizerEditField',
+    'DiffusionIdentityAssigneeSearchField' => 'PhabricatorSearchTokenizerField',
+    'DiffusionIdentityEditController' => 'DiffusionController',
+    'DiffusionIdentityListController' => 'DiffusionController',
+    'DiffusionIdentityUnassignedDatasource' => 'PhabricatorTypeaheadDatasource',
+    'DiffusionIdentityViewController' => 'DiffusionController',
     'DiffusionInlineCommentController' => 'PhabricatorInlineCommentController',
     'DiffusionInlineCommentPreviewController' => 'PhabricatorInlineCommentPreviewController',
     'DiffusionInternalGitRawDiffQueryConduitAPIMethod' => 'DiffusionQueryConduitAPIMethod',
@@ -6264,6 +6290,8 @@
     'DiffusionRepositoryEditUpdateController' => 'DiffusionRepositoryManageController',
     'DiffusionRepositoryFunctionDatasource' => 'PhabricatorTypeaheadCompositeDatasource',
     'DiffusionRepositoryHistoryManagementPanel' => 'DiffusionRepositoryManagementPanel',
+    'DiffusionRepositoryIdentityEditor' => 'PhabricatorApplicationTransactionEditor',
+    'DiffusionRepositoryIdentitySearchEngine' => 'PhabricatorApplicationSearchEngine',
     'DiffusionRepositoryListController' => 'DiffusionController',
     'DiffusionRepositoryManageController' => 'DiffusionController',
     'DiffusionRepositoryManagePanelsController' => 'DiffusionRepositoryManageController',
@@ -9961,6 +9989,20 @@
     'PhabricatorRepositoryGitLFSRefQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorRepositoryGraphCache' => 'Phobject',
     'PhabricatorRepositoryGraphStream' => 'Phobject',
+    'PhabricatorRepositoryIdentity' => array(
+      'PhabricatorRepositoryDAO',
+      'PhabricatorPolicyInterface',
+      'PhabricatorApplicationTransactionInterface',
+    ),
+    'PhabricatorRepositoryIdentityAssignTransaction' => 'PhabricatorRepositoryIdentityTransactionType',
+    'PhabricatorRepositoryIdentityChangeWorker' => 'PhabricatorWorker',
+    'PhabricatorRepositoryIdentityEditEngine' => 'PhabricatorEditEngine',
+    'PhabricatorRepositoryIdentityFerretEngine' => 'PhabricatorFerretEngine',
+    'PhabricatorRepositoryIdentityPHIDType' => 'PhabricatorPHIDType',
+    'PhabricatorRepositoryIdentityQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
+    'PhabricatorRepositoryIdentityTransaction' => 'PhabricatorModularTransaction',
+    'PhabricatorRepositoryIdentityTransactionQuery' => 'PhabricatorApplicationTransactionQuery',
+    'PhabricatorRepositoryIdentityTransactionType' => 'PhabricatorModularTransactionType',
     'PhabricatorRepositoryManagementCacheWorkflow' => 'PhabricatorRepositoryManagementWorkflow',
     'PhabricatorRepositoryManagementClusterizeWorkflow' => 'PhabricatorRepositoryManagementWorkflow',
     'PhabricatorRepositoryManagementDiscoverWorkflow' => 'PhabricatorRepositoryManagementWorkflow',
diff --git a/src/applications/diffusion/application/PhabricatorDiffusionApplication.php b/src/applications/diffusion/application/PhabricatorDiffusionApplication.php
--- a/src/applications/diffusion/application/PhabricatorDiffusionApplication.php
+++ b/src/applications/diffusion/application/PhabricatorDiffusionApplication.php
@@ -124,6 +124,15 @@
         '(?P<repositoryCallsign>[A-Z]+)' => $repository_routes,
         '(?P<repositoryID>[1-9]\d*)' => $repository_routes,
 
+        'identity/' => array(
+          $this->getQueryRoutePattern() =>
+            'DiffusionIdentityListController',
+          $this->getEditRoutePattern('edit/') =>
+            'DiffusionIdentityEditController',
+          'view/(?P<id>[^/]+)/' =>
+            'DiffusionIdentityViewController',
+        ),
+
         'inline/' => array(
           'edit/(?P<phid>[^/]+)/' => 'DiffusionInlineCommentController',
           'preview/(?P<phid>[^/]+)/'
diff --git a/src/applications/diffusion/controller/DiffusionIdentityEditController.php b/src/applications/diffusion/controller/DiffusionIdentityEditController.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/controller/DiffusionIdentityEditController.php
@@ -0,0 +1,12 @@
+<?php
+
+final class DiffusionIdentityEditController
+  extends DiffusionController {
+
+  public function handleRequest(AphrontRequest $request) {
+    return id(new PhabricatorRepositoryIdentityEditEngine())
+      ->setController($this)
+      ->buildResponse();
+  }
+
+}
diff --git a/src/applications/diffusion/controller/DiffusionIdentityListController.php b/src/applications/diffusion/controller/DiffusionIdentityListController.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/controller/DiffusionIdentityListController.php
@@ -0,0 +1,22 @@
+<?php
+
+final class DiffusionIdentityListController
+  extends DiffusionController {
+
+  public function handleRequest(AphrontRequest $request) {
+    return id(new DiffusionRepositoryIdentitySearchEngine())
+      ->setController($this)
+      ->buildResponse();
+  }
+
+  protected function buildApplicationCrumbs() {
+    $crumbs = parent::buildApplicationCrumbs();
+
+    id(new PhabricatorRepositoryIdentityEditEngine())
+      ->setViewer($this->getViewer())
+      ->addActionToCrumbs($crumbs);
+
+    return $crumbs;
+  }
+
+}
diff --git a/src/applications/diffusion/controller/DiffusionIdentityViewController.php b/src/applications/diffusion/controller/DiffusionIdentityViewController.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/controller/DiffusionIdentityViewController.php
@@ -0,0 +1,136 @@
+<?php
+
+final class DiffusionIdentityViewController
+  extends DiffusionController {
+
+  public function handleRequest(AphrontRequest $request) {
+    $viewer = $request->getViewer();
+
+    $id = $request->getURIData('id');
+    $identity = id(new PhabricatorRepositoryIdentityQuery())
+      ->setViewer($viewer)
+      ->withIDs(array($id))
+      ->executeOne();
+    if (!$identity) {
+      return new Aphront404Response();
+    }
+
+    $title = pht('Identity %d', $identity->getID());
+
+    $curtain = $this->buildCurtain($identity);
+
+    $header = id(new PHUIHeaderView())
+      ->setUser($viewer)
+      ->setHeader($identity->getIdentityShortName())
+      ->setHeaderIcon('fa-globe')
+      ->setPolicyObject($identity);
+
+    $crumbs = $this->buildApplicationCrumbs();
+    $crumbs->addTextCrumb($identity->getID());
+    $crumbs->setBorder(true);
+
+    $timeline = $this->buildTransactionTimeline(
+      $identity,
+      new PhabricatorRepositoryIdentityTransactionQuery());
+    $timeline->setShouldTerminate(true);
+
+    $properties = $this->buildPropertyList($identity);
+
+    $view = id(new PHUITwoColumnView())
+      ->setHeader($header)
+      ->setCurtain($curtain)
+      ->setMainColumn(array(
+          $properties,
+          $timeline,
+        ));
+
+    return $this->newPage()
+      ->setTitle($title)
+      ->setCrumbs($crumbs)
+      ->appendChild(
+        array(
+          $view,
+      ));
+  }
+
+  private function buildCurtain(PhabricatorRepositoryIdentity $identity) {
+    $viewer = $this->getViewer();
+
+    $can_edit = PhabricatorPolicyFilter::hasCapability(
+      $viewer,
+      $identity,
+      PhabricatorPolicyCapability::CAN_EDIT);
+
+    $id = $identity->getID();
+    $edit_uri = $this->getApplicationURI("identity/edit/{$id}/");
+
+    $curtain = $this->newCurtainView($identity);
+
+    $curtain->addAction(
+      id(new PhabricatorActionView())
+        ->setIcon('fa-pencil')
+        ->setName(pht('Edit Identity'))
+        ->setHref($edit_uri)
+        ->setWorkflow(!$can_edit)
+        ->setDisabled(!$can_edit));
+
+    return $curtain;
+  }
+
+  private function buildPropertyList(
+    PhabricatorRepositoryIdentity $identity) {
+
+    $viewer = $this->getViewer();
+
+    $properties = id(new PHUIPropertyListView())
+      ->setUser($viewer);
+
+    $effective_phid = $identity->getCurrentEffectiveUserPHID();
+    $automatic_phid = $identity->getAutomaticGuessedUserPHID();
+    $manual_phid = $identity->getManuallySetUserPHID();
+
+    if ($effective_phid) {
+      $tag = id(new PHUITagView())
+        ->setType(PHUITagView::TYPE_SHADE)
+        ->setColor('green')
+        ->setIcon('fa-check')
+        ->setName('Assigned');
+    } else {
+      $tag = id(new PHUITagView())
+        ->setType(PHUITagView::TYPE_SHADE)
+        ->setColor('indigo')
+        ->setIcon('fa-bomb')
+        ->setName('Unassigned');
+    }
+    $properties->addProperty(
+      pht('Effective User'),
+      $this->buildPropertyValue($effective_phid));
+    $properties->addProperty(
+      pht('Automatically Detected User'),
+      $this->buildPropertyValue($automatic_phid));
+    $properties->addProperty(
+      pht('Manually Set User'),
+      $this->buildPropertyValue($manual_phid));
+
+    $header = id(new PHUIHeaderView())
+      ->setHeader(array(pht('Identity Assignments'), $tag));
+
+    return id(new PHUIObjectBoxView())
+      ->setHeader($header)
+      ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
+      ->addPropertyList($properties);
+  }
+
+  private function buildPropertyValue($value) {
+    $viewer = $this->getViewer();
+
+    // TODO: there must be a way to render the fancy "Unassigned" tag
+    if ($value == DiffusionIdentityUnassignedDatasource::FUNCTION_TOKEN) {
+      return pht('<Explicitly Unassigned>');
+    } else if (!$value) {
+      return null;
+    } else {
+      return $viewer->renderHandle($value);
+    }
+  }
+}
diff --git a/src/applications/diffusion/editfield/DiffusionIdentityAssigneeEditField.php b/src/applications/diffusion/editfield/DiffusionIdentityAssigneeEditField.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/editfield/DiffusionIdentityAssigneeEditField.php
@@ -0,0 +1,22 @@
+<?php
+
+final class DiffusionIdentityAssigneeEditField
+  extends PhabricatorTokenizerEditField {
+
+  protected function newDatasource() {
+    return new DiffusionIdentityAssigneeDatasource();
+  }
+
+  protected function newHTTPParameterType() {
+    return new AphrontUserListHTTPParameterType();
+  }
+
+  protected function newConduitParameterType() {
+    if ($this->getIsSingleValue()) {
+      return new ConduitUserParameterType();
+    } else {
+      return new ConduitUserListParameterType();
+    }
+  }
+
+}
diff --git a/src/applications/diffusion/editor/DiffusionRepositoryIdentityEditor.php b/src/applications/diffusion/editor/DiffusionRepositoryIdentityEditor.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/editor/DiffusionRepositoryIdentityEditor.php
@@ -0,0 +1,26 @@
+<?php
+
+final class DiffusionRepositoryIdentityEditor
+  extends PhabricatorApplicationTransactionEditor {
+
+  public function getEditorObjectsDescription() {
+    return pht('Repository Identity');
+  }
+
+  public function getCreateObjectTitle($author, $object) {
+    return pht('%s created this identity.', $author);
+  }
+
+  public function getCreateObjectTitleForFeed($author, $object) {
+    return pht('%s created %s.', $author, $object);
+  }
+
+  protected function supportsSearch() {
+    return true;
+  }
+
+  public function getEditorApplicationClass() {
+    return 'PhabricatorDiffusionApplication';
+  }
+
+}
diff --git a/src/applications/diffusion/query/DiffusionRepositoryIdentitySearchEngine.php b/src/applications/diffusion/query/DiffusionRepositoryIdentitySearchEngine.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/query/DiffusionRepositoryIdentitySearchEngine.php
@@ -0,0 +1,108 @@
+<?php
+
+final class DiffusionRepositoryIdentitySearchEngine
+  extends PhabricatorApplicationSearchEngine {
+
+  public function getResultTypeDescription() {
+    return pht('Repository Identities');
+  }
+
+  public function getApplicationClassName() {
+    return 'PhabricatorDiffusionApplication';
+  }
+
+  public function newQuery() {
+    return new PhabricatorRepositoryIdentityQuery();
+  }
+
+  protected function buildCustomSearchFields() {
+    return array(
+      id(new DiffusionIdentityAssigneeSearchField())
+        ->setLabel(pht('Assigned To'))
+        ->setKey('assignee')
+        ->setDescription(pht('Search for identities by assignee.')),
+      id(new PhabricatorSearchTextField())
+        ->setLabel(pht('Identity Contains'))
+        ->setKey('match')
+        ->setDescription(pht('Search for identities by substring.')),
+      id(new PhabricatorSearchThreeStateField())
+        ->setLabel(pht('Is Assigned'))
+        ->setKey('hasEffectivePHID')
+        ->setOptions(
+          pht('(Show All)'),
+          pht('Show Only Assigned Identities'),
+          pht('Show Only Unassigned Identities')),
+    );
+  }
+
+  protected function buildQueryFromParameters(array $map) {
+    $query = $this->newQuery();
+
+    if ($map['hasEffectivePHID'] !== null) {
+      $query->withHasEffectivePHID($map['hasEffectivePHID']);
+    }
+
+    if ($map['match'] !== null) {
+      $query->withIdentityNameLike($map['match']);
+    }
+
+    if ($map['assignee'] !== null) {
+      $query->withAssigneePHIDs($map['assignee']);
+    }
+
+    return $query;
+  }
+
+  protected function getURI($path) {
+    return '/diffusion/identity/'.$path;
+  }
+
+  protected function getBuiltinQueryNames() {
+    $names = array(
+      'all' => pht('All Identities'),
+    );
+
+    return $names;
+  }
+
+  public function buildSavedQueryFromBuiltin($query_key) {
+
+    $query = $this->newSavedQuery();
+    $query->setQueryKey($query_key);
+
+    switch ($query_key) {
+      case 'all':
+        return $query;
+    }
+
+    return parent::buildSavedQueryFromBuiltin($query_key);
+  }
+
+  protected function renderResultList(
+    array $identities,
+    PhabricatorSavedQuery $query,
+    array $handles) {
+    assert_instances_of($identities, 'PhabricatorRepositoryIdentity');
+
+    $viewer = $this->requireViewer();
+
+    $list = new PHUIObjectItemListView();
+    $list->setUser($viewer);
+    foreach ($identities as $identity) {
+      $item = id(new PHUIObjectItemView())
+        ->setObjectName(pht('Identity %d', $identity->getID()))
+        ->setHeader($identity->getIdentityShortName())
+        ->setHref($identity->getURI())
+        ->setObject($identity);
+
+      $list->addItem($item);
+    }
+
+    $result = new PhabricatorApplicationSearchResultView();
+    $result->setObjectList($list);
+    $result->setNoDataString(pht('No Identities found.'));
+
+    return $result;
+  }
+
+}
diff --git a/src/applications/diffusion/searchfield/DiffusionIdentityAssigneeSearchField.php b/src/applications/diffusion/searchfield/DiffusionIdentityAssigneeSearchField.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/searchfield/DiffusionIdentityAssigneeSearchField.php
@@ -0,0 +1,22 @@
+<?php
+
+final class DiffusionIdentityAssigneeSearchField
+  extends PhabricatorSearchTokenizerField {
+
+  protected function getDefaultValue() {
+    return array();
+  }
+
+  protected function getValueFromRequest(AphrontRequest $request, $key) {
+    return $this->getUsersFromRequest($request, $key);
+  }
+
+  protected function newDatasource() {
+    return new DiffusionIdentityAssigneeDatasource();
+  }
+
+  protected function newConduitParameterType() {
+    return new ConduitUserListParameterType();
+  }
+
+}
diff --git a/src/applications/diffusion/typeahead/DiffusionIdentityAssigneeDatasource.php b/src/applications/diffusion/typeahead/DiffusionIdentityAssigneeDatasource.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/typeahead/DiffusionIdentityAssigneeDatasource.php
@@ -0,0 +1,22 @@
+<?php
+
+final class DiffusionIdentityAssigneeDatasource
+  extends PhabricatorTypeaheadCompositeDatasource {
+
+  public function getBrowseTitle() {
+    return pht('Browse Assignee');
+  }
+
+  public function getPlaceholderText() {
+    return pht('Type a username or function...');
+  }
+
+  public function getComponentDatasources() {
+    return array(
+      new PhabricatorViewerDatasource(),
+      new PhabricatorPeopleDatasource(),
+      new DiffusionIdentityUnassignedDatasource(),
+    );
+  }
+
+}
diff --git a/src/applications/diffusion/typeahead/DiffusionIdentityUnassignedDatasource.php b/src/applications/diffusion/typeahead/DiffusionIdentityUnassignedDatasource.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/typeahead/DiffusionIdentityUnassignedDatasource.php
@@ -0,0 +1,77 @@
+<?php
+
+final class DiffusionIdentityUnassignedDatasource
+  extends PhabricatorTypeaheadDatasource {
+
+  const FUNCTION_TOKEN = 'unassigned()';
+
+  public function getBrowseTitle() {
+    return pht('Browse Explicitly Unassigned');
+  }
+
+  public function getPlaceholderText() {
+    return pht('Type "unassigned"...');
+  }
+
+  public function getDatasourceApplicationClass() {
+    return 'PhabricatorDiffusionApplication';
+  }
+
+  public function getDatasourceFunctions() {
+    return array(
+      'unassigned' => array(
+        'name' => pht('Explicitly Unassigned'),
+        'summary' => pht('Find results which are not assigned.'),
+        'description' => pht(
+          "This function includes results which have been explicitly ".
+          "unassigned. Use a query like this to find explicitly ".
+          "unassigned results:\n\n%s\n\n".
+          "If you combine this function with other functions, the query will ".
+          "return results which match the other selectors //or// have no ".
+          "assignee. For example, this query will find results which are ".
+          "assigned to `alincoln`, and will also find results which have been ".
+          "unassigned:\n\n%s",
+          '> unassigned()',
+          '> alincoln, unassigned()'),
+      ),
+    );
+  }
+
+  public function loadResults() {
+    $results = array(
+      $this->buildUnassignedResult(),
+    );
+    return $this->filterResultsAgainstTokens($results);
+  }
+
+  protected function evaluateFunction($function, array $argv_list) {
+    $results = array();
+
+    foreach ($argv_list as $argv) {
+      $results[] = self::FUNCTION_TOKEN;
+    }
+
+    return $results;
+  }
+
+  public function renderFunctionTokens($function, array $argv_list) {
+    $results = array();
+    foreach ($argv_list as $argv) {
+      $results[] = PhabricatorTypeaheadTokenView::newFromTypeaheadResult(
+        $this->buildUnassignedResult());
+    }
+    return $results;
+  }
+
+  private function buildUnassignedResult() {
+    $name = pht('Unassigned');
+    return $this->newFunctionResult()
+      ->setName($name.' unassigned')
+      ->setDisplayName($name)
+      ->setIcon('fa-ban')
+      ->setPHID('unassigned()')
+      ->setUnique(true)
+      ->addAttribute(pht('Select results with no owner.'));
+  }
+
+}
diff --git a/src/applications/people/editor/PhabricatorUserEditor.php b/src/applications/people/editor/PhabricatorUserEditor.php
--- a/src/applications/people/editor/PhabricatorUserEditor.php
+++ b/src/applications/people/editor/PhabricatorUserEditor.php
@@ -420,6 +420,11 @@
       $user->endWriteLocking();
     $user->saveTransaction();
 
+    // Try and match this new address against unclaimed `RepositoryIdentity`s
+    PhabricatorWorker::scheduleTask(
+      'PhabricatorRepositoryIdentityChangeWorker',
+      array('userPHID' => $user->getPHID()));
+
     return $this;
   }
 
diff --git a/src/applications/repository/engine/PhabricatorRepositoryIdentityEditEngine.php b/src/applications/repository/engine/PhabricatorRepositoryIdentityEditEngine.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/engine/PhabricatorRepositoryIdentityEditEngine.php
@@ -0,0 +1,91 @@
+<?php
+
+final class PhabricatorRepositoryIdentityEditEngine
+  extends PhabricatorEditEngine {
+
+  const ENGINECONST = 'repository.identity';
+
+  public function isEngineConfigurable() {
+    return false;
+  }
+
+  public function getEngineName() {
+    return pht('Repository Identities');
+  }
+
+  public function getSummaryHeader() {
+    return pht('Edit Repository Identity Configurations');
+  }
+
+  public function getSummaryText() {
+    return pht('This engine is used to edit Repository identities.');
+  }
+
+  public function getEngineApplicationClass() {
+    return 'PhabricatorDiffusionApplication';
+  }
+
+  protected function newEditableObject() {
+    return new PhabricatorRepositoryIdentity();
+  }
+
+  protected function newObjectQuery() {
+    return new PhabricatorRepositoryIdentityQuery();
+  }
+
+  protected function getObjectCreateTitleText($object) {
+    return pht('Create Identity');
+  }
+
+  protected function getObjectCreateButtonText($object) {
+    return pht('Create Identity');
+  }
+
+  protected function getObjectEditTitleText($object) {
+    return pht('Edit Identity: %s', $object->getIdentityShortName());
+  }
+
+  protected function getObjectEditShortText($object) {
+    return pht('Edit Identity');
+  }
+
+  protected function getObjectCreateShortText() {
+    return pht('Create Identity');
+  }
+
+  protected function getObjectName() {
+    return pht('Identity');
+  }
+
+  protected function getEditorURI() {
+    return '/diffusion/identity/edit/';
+  }
+
+  protected function getObjectCreateCancelURI($object) {
+    return '/diffusion/identity/';
+  }
+
+  protected function getObjectViewURI($object) {
+    return $object->getURI();
+  }
+
+  protected function getCreateNewObjectPolicy() {
+    return PhabricatorPolicies::POLICY_USER;
+  }
+
+  protected function buildCustomEditFields($object) {
+    return array(
+      id(new DiffusionIdentityAssigneeEditField())
+        ->setKey('manuallySetUserPHID')
+        ->setLabel(pht('Assigned To'))
+        ->setDescription(pht('Override this identity\'s assignment.'))
+        ->setTransactionType(
+          PhabricatorRepositoryIdentityAssignTransaction::TRANSACTIONTYPE)
+        ->setIsCopyable(true)
+        ->setIsNullable(true)
+        ->setSingleValue($object->getManuallySetUserPHID()),
+
+    );
+  }
+
+}
diff --git a/src/applications/repository/phid/PhabricatorRepositoryIdentityPHIDType.php b/src/applications/repository/phid/PhabricatorRepositoryIdentityPHIDType.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/phid/PhabricatorRepositoryIdentityPHIDType.php
@@ -0,0 +1,33 @@
+<?php
+
+final class PhabricatorRepositoryIdentityPHIDType
+  extends PhabricatorPHIDType {
+
+  const TYPECONST = 'RIDT';
+
+  public function getTypeName() {
+    return pht('Repository Identity');
+  }
+
+  public function newObject() {
+    return new PhabricatorRepositoryIdentity();
+  }
+
+  public function getPHIDTypeApplicationClass() {
+    return 'PhabricatorDiffusionApplication';
+  }
+
+  protected function buildQueryForObjects(
+    PhabricatorObjectQuery $query,
+    array $phids) {
+
+    return id(new PhabricatorRepositoryIdentityQuery())
+      ->withPHIDs($phids);
+  }
+
+  public function loadHandles(
+    PhabricatorHandleQuery $query,
+    array $handles,
+    array $objects) {}
+
+}
diff --git a/src/applications/repository/query/PhabricatorRepositoryIdentityQuery.php b/src/applications/repository/query/PhabricatorRepositoryIdentityQuery.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/query/PhabricatorRepositoryIdentityQuery.php
@@ -0,0 +1,132 @@
+<?php
+
+final class PhabricatorRepositoryIdentityQuery
+  extends PhabricatorCursorPagedPolicyAwareQuery {
+
+  private $ids;
+  private $phids;
+  private $identityNames;
+  private $emailAddress;
+  private $assigneePHIDs;
+  private $identityNameLike;
+  private $hasEffectivePHID;
+
+  public function withIDs(array $ids) {
+    $this->ids = $ids;
+    return $this;
+  }
+
+  public function withPHIDs(array $phids) {
+    $this->phids = $phids;
+    return $this;
+  }
+
+  public function withIdentityNames(array $names) {
+    $this->identityNames = $names;
+    return $this;
+  }
+
+  public function withIdentityNameLike($name_like) {
+    $this->identityNameLike = $name_like;
+    return $this;
+  }
+
+  public function withEmailAddress($address) {
+    $this->emailAddress = $address;
+    return $this;
+  }
+
+  public function withAssigneePHIDs(array $assignees) {
+    $this->assigneePHIDs = $assignees;
+    return $this;
+  }
+
+  public function withHasEffectivePHID($has_effective_phid) {
+    $this->hasEffectivePHID = $has_effective_phid;
+    return $this;
+  }
+
+  public function newResultObject() {
+    return new PhabricatorRepositoryIdentity();
+  }
+
+  protected function getPrimaryTableAlias() {
+     return 'repository_identity';
+   }
+
+  protected function loadPage() {
+    return $this->loadStandardPage($this->newResultObject());
+  }
+
+  protected function buildWhereClauseParts(AphrontDatabaseConnection $conn) {
+    $where = parent::buildWhereClauseParts($conn);
+
+    if ($this->ids !== null) {
+      $where[] = qsprintf(
+        $conn,
+        'repository_identity.id IN (%Ld)',
+        $this->ids);
+    }
+
+    if ($this->phids !== null) {
+      $where[] = qsprintf(
+        $conn,
+        'repository_identity.phid IN (%Ls)',
+        $this->phids);
+    }
+
+    if ($this->assigneePHIDs !== null) {
+      $where[] = qsprintf(
+        $conn,
+        'repository_identity.currentEffectiveUserPHID IN (%Ls)',
+        $this->assigneePHIDs);
+    }
+
+    if ($this->hasEffectivePHID !== null) {
+
+      if ($this->hasEffectivePHID) {
+        $where[] = qsprintf(
+          $conn,
+          'repository_identity.currentEffectiveUserPHID IS NOT NULL');
+      } else {
+        $where[] = qsprintf(
+          $conn,
+          'repository_identity.currentEffectiveUserPHID IS NULL');
+      }
+    }
+
+    if ($this->identityNames !== null) {
+      $name_hashes = array();
+      foreach ($this->identityNames as $name) {
+        $name_hashes[] = PhabricatorHash::digestForIndex($name);
+      }
+
+      $where[] = qsprintf(
+        $conn,
+        'repository_identity.identityNameHash IN (%Ls)',
+        $name_hashes);
+    }
+
+    if ($this->emailAddress !== null) {
+      $identity_style = "<{$this->emailAddress}>";
+      $where[] = qsprintf(
+        $conn,
+        'repository_identity.identityNameRaw LIKE %<',
+        $identity_style);
+    }
+
+    if ($this->identityNameLike != null) {
+      $where[] = qsprintf(
+        $conn,
+        'repository_identity.identityNameRaw LIKE %~',
+        $this->identityNameLike);
+    }
+
+    return $where;
+  }
+
+  public function getQueryApplicationClass() {
+    return 'PhabricatorDiffusionApplication';
+  }
+
+}
diff --git a/src/applications/repository/query/PhabricatorRepositoryIdentityTransactionQuery.php b/src/applications/repository/query/PhabricatorRepositoryIdentityTransactionQuery.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/query/PhabricatorRepositoryIdentityTransactionQuery.php
@@ -0,0 +1,10 @@
+<?php
+
+final class PhabricatorRepositoryIdentityTransactionQuery
+  extends PhabricatorApplicationTransactionQuery {
+
+  public function getTemplateApplicationTransaction() {
+    return new PhabricatorRepositoryIdentityTransaction();
+  }
+
+}
diff --git a/src/applications/repository/search/PhabricatorRepositoryIdentityFerretEngine.php b/src/applications/repository/search/PhabricatorRepositoryIdentityFerretEngine.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/search/PhabricatorRepositoryIdentityFerretEngine.php
@@ -0,0 +1,18 @@
+<?php
+
+final class PhabricatorRepositoryIdentityFerretEngine
+  extends PhabricatorFerretEngine {
+
+  public function getApplicationName() {
+    return 'repository';
+  }
+
+  public function getScopeName() {
+    return 'identity';
+  }
+
+  public function newSearchEngine() {
+    return new DiffusionRepositoryIdentitySearchEngine();
+  }
+
+}
diff --git a/src/applications/repository/storage/PhabricatorRepositoryCommit.php b/src/applications/repository/storage/PhabricatorRepositoryCommit.php
--- a/src/applications/repository/storage/PhabricatorRepositoryCommit.php
+++ b/src/applications/repository/storage/PhabricatorRepositoryCommit.php
@@ -21,6 +21,8 @@
 
   protected $repositoryID;
   protected $phid;
+  protected $authorIdentityPHID;
+  protected $committerIdentityPHID;
   protected $commitIdentifier;
   protected $epoch;
   protected $mailKey;
@@ -113,6 +115,8 @@
         'commitIdentifier' => 'text40',
         'mailKey' => 'bytes20',
         'authorPHID' => 'phid?',
+        'authorIdentityPHID' => 'phid?',
+        'committerIdentityPHID' => 'phid?',
         'auditStatus' => 'uint32',
         'summary' => 'text255',
         'importStatus' => 'uint32',
diff --git a/src/applications/repository/storage/PhabricatorRepositoryIdentity.php b/src/applications/repository/storage/PhabricatorRepositoryIdentity.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/storage/PhabricatorRepositoryIdentity.php
@@ -0,0 +1,119 @@
+<?php
+
+final class PhabricatorRepositoryIdentity
+  extends PhabricatorRepositoryDAO
+  implements
+    PhabricatorPolicyInterface,
+    PhabricatorApplicationTransactionInterface {
+
+  protected $authorPHID;
+  protected $identityNameHash;
+  protected $identityNameRaw;
+  protected $identityNameEncoding;
+  protected $automaticGuessedUserPHID;
+  protected $manuallySetUserPHID;
+  protected $currentEffectiveUserPHID;
+
+  protected function getConfiguration() {
+    return array(
+      self::CONFIG_AUX_PHID => true,
+      self::CONFIG_BINARY => array(
+        'identityNameRaw' => true,
+      ),
+      self::CONFIG_COLUMN_SCHEMA => array(
+        'identityNameHash' => 'bytes12',
+        'identityNameEncoding' => 'text16?',
+        'automaticGuessedUserPHID' => 'phid?',
+        'manuallySetUserPHID' => 'phid?',
+        'currentEffectiveUserPHID' => 'phid?',
+      ),
+      self::CONFIG_KEY_SCHEMA => array(
+        'key_identity' => array(
+          'columns' => array('identityNameHash'),
+          'unique' => true,
+        ),
+      ),
+    ) + parent::getConfiguration();
+  }
+
+  public function getPHIDType() {
+    return PhabricatorRepositoryIdentityPHIDType::TYPECONST;
+  }
+
+  public function setIdentityName($name_raw) {
+    $this->setIdentityNameRaw($name_raw);
+    $this->setIdentityNameHash(PhabricatorHash::digestForIndex($name_raw));
+    $this->setIdentityNameEncoding($this->detectEncodingForStorage($name_raw));
+
+    return $this;
+  }
+
+  public function getIdentityName() {
+    return $this->getUTF8StringFromStorage(
+      $this->getIdentityNameRaw(),
+      $this->getIdentityNameEncoding());
+  }
+
+  public function getIdentityShortName() {
+    // TODO
+    return $this->getIdentityName();
+  }
+
+  public function getURI() {
+    return '/diffusion/identity/view/'.$this->getID().'/';
+  }
+
+  public function save() {
+    if ($this->manuallySetUserPHID) {
+      $this->currentEffectiveUserPHID = $this->manuallySetUserPHID;
+    } else {
+      $this->currentEffectiveUserPHID = $this->automaticGuessedUserPHID;
+    }
+
+    return parent::save();
+  }
+
+
+/* -(  PhabricatorPolicyInterface  )----------------------------------------- */
+
+
+  public function getCapabilities() {
+    return array(
+      PhabricatorPolicyCapability::CAN_VIEW,
+      PhabricatorPolicyCapability::CAN_EDIT,
+    );
+  }
+
+  public function getPolicy($capability) {
+    return PhabricatorPolicies::getMostOpenPolicy();
+  }
+
+  public function hasAutomaticCapability(
+    $capability, PhabricatorUser $viewer) {
+    return false;
+  }
+
+
+/* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
+
+
+  public function getApplicationTransactionEditor() {
+    return new DiffusionRepositoryIdentityEditor();
+  }
+
+  public function getApplicationTransactionObject() {
+    return $this;
+  }
+
+  public function getApplicationTransactionTemplate() {
+    return new PhabricatorRepositoryIdentityTransaction();
+  }
+
+  public function willRenderTimeline(
+    PhabricatorApplicationTransactionView $timeline,
+    AphrontRequest $request) {
+
+    return $timeline;
+  }
+
+}
diff --git a/src/applications/repository/storage/PhabricatorRepositoryIdentityTransaction.php b/src/applications/repository/storage/PhabricatorRepositoryIdentityTransaction.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/storage/PhabricatorRepositoryIdentityTransaction.php
@@ -0,0 +1,18 @@
+<?php
+
+final class PhabricatorRepositoryIdentityTransaction
+  extends PhabricatorModularTransaction {
+
+  public function getApplicationTransactionType() {
+    return PhabricatorRepositoryIdentityPHIDType::TYPECONST;
+  }
+
+  public function getBaseTransactionClass() {
+    return 'PhabricatorRepositoryIdentityTransactionType';
+  }
+
+  public function getApplicationName() {
+    return 'repository';
+  }
+
+}
diff --git a/src/applications/repository/worker/PhabricatorRepositoryIdentityChangeWorker.php b/src/applications/repository/worker/PhabricatorRepositoryIdentityChangeWorker.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/worker/PhabricatorRepositoryIdentityChangeWorker.php
@@ -0,0 +1,34 @@
+<?php
+
+final class PhabricatorRepositoryIdentityChangeWorker
+extends PhabricatorWorker {
+
+  protected function doWork() {
+    $viewer = PhabricatorUser::getOmnipotentUser();
+
+    $task_data = $this->getTaskData();
+    $user_phid = idx($task_data, 'userPHID');
+
+    $user = id(new PhabricatorPeopleQuery())
+      ->withPHIDs(array($user_phid))
+      ->setViewer($viewer)
+      ->executeOne();
+
+    $emails = id(new PhabricatorUserEmail())->loadAllWhere(
+      'userPHID = %s ORDER BY address',
+      $user->getPHID());
+
+    foreach ($emails as $email) {
+      $identities = id(new PhabricatorRepositoryIdentityQuery())
+        ->setViewer($viewer)
+        ->withEmailAddress($email->getAddress())
+        ->execute();
+
+      foreach ($identities as $identity) {
+        $identity->setAutomaticGuessedUserPHID($user->getPHID())
+          ->save();
+      }
+    }
+  }
+
+}
diff --git a/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php b/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php
--- a/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php
+++ b/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php
@@ -66,6 +66,34 @@
     $committer = $ref->getCommitter();
     $hashes = $ref->getHashes();
 
+    $author_identity = id(new PhabricatorRepositoryIdentityQuery())
+      ->setViewer(PhabricatorUser::getOmnipotentUser())
+      ->withIdentityNames(array($author))
+      ->executeOne();
+
+    if (!$author_identity) {
+      $author_identity = id(new PhabricatorRepositoryIdentity())
+        ->setAuthorPHID($commit->getPHID())
+        ->setIdentityName($author)
+        ->setAutomaticGuessedUserPHID(
+          $this->resolveUserPHID($commit, $author))
+        ->save();
+    }
+
+    $committer_identity = id(new PhabricatorRepositoryIdentityQuery())
+      ->setViewer(PhabricatorUser::getOmnipotentUser())
+      ->withIdentityNames(array($committer))
+      ->executeOne();
+
+    if (!$committer_identity) {
+      $committer_identity = id(new PhabricatorRepositoryIdentity())
+        ->setAuthorPHID($commit->getPHID())
+        ->setIdentityName($committer)
+        ->setAutomaticGuessedUserPHID(
+          $this->resolveUserPHID($commit, $committer))
+        ->save();
+    }
+
     $data = id(new PhabricatorRepositoryCommitData())->loadOneWhere(
       'commitID = %d',
       $commit->getID());
@@ -81,6 +109,8 @@
     $data->setCommitDetail('authorName', $ref->getAuthorName());
     $data->setCommitDetail('authorEmail', $ref->getAuthorEmail());
 
+    $data->setCommitDetail(
+      'authorIdentityPHID', $author_identity->getPHID());
     $data->setCommitDetail(
       'authorPHID',
       $this->resolveUserPHID($commit, $author));
@@ -96,6 +126,8 @@
       $data->setCommitDetail(
         'committerPHID',
         $this->resolveUserPHID($commit, $committer));
+      $data->setCommitDetail(
+        'committerIdentityPHID', $committer_identity->getPHID());
     }
 
     $repository = $this->repository;
@@ -133,6 +165,9 @@
       $commit->setAuthorPHID($author_phid);
     }
 
+    $commit->setAuthorIdentityPHID($author_identity->getPHID());
+    $commit->setCommitterIdentityPHID($committer_identity->getPHID());
+
     $commit->setSummary($data->getSummary());
     $commit->save();
 
diff --git a/src/applications/repository/xaction/PhabricatorRepositoryIdentityAssignTransaction.php b/src/applications/repository/xaction/PhabricatorRepositoryIdentityAssignTransaction.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/xaction/PhabricatorRepositoryIdentityAssignTransaction.php
@@ -0,0 +1,70 @@
+<?php
+
+final class PhabricatorRepositoryIdentityAssignTransaction
+  extends PhabricatorRepositoryIdentityTransactionType {
+
+  const TRANSACTIONTYPE = 'repository:identity:assign';
+
+  public function generateOldValue($object) {
+    return nonempty($object->getManuallySetUserPHID(), null);
+  }
+
+  public function applyInternalEffects($object, $value) {
+    $object->setManuallySetUserPHID($value);
+  }
+
+  public function getTitle() {
+    $old = $this->getOldValue();
+    $new = $this->getNewValue();
+
+    if (!$old) {
+      return pht(
+        '%s assigned this identity to %s.',
+        $this->renderAuthor(),
+        $this->renderHandle($new));
+    } else if (!$new) {
+      return pht(
+        '%s removed %s as the assignee of this identity.',
+        $this->renderAuthor(),
+        $this->renderHandle($old));
+    } else {
+      return pht(
+        '%s changed the assigned user for this identity from %s to %s.',
+        $this->renderAuthor(),
+        $this->renderHandle($old),
+        $this->renderHandle($new));
+    }
+  }
+
+  public function validateTransactions($object, array $xactions) {
+    $errors = array();
+
+    foreach ($xactions as $xaction) {
+      $old = $xaction->getOldValue();
+      $new = $xaction->getNewValue();
+      if (!strlen($new)) {
+        continue;
+      }
+
+      if ($new === $old) {
+        continue;
+      }
+
+      $assignee_list = id(new PhabricatorPeopleQuery())
+        ->setViewer($this->getActor())
+        ->withPHIDs(array($new))
+        ->execute();
+
+      // TODO: turn this back on when I figure out how to check for
+      // 'unassigned()'
+
+      // if (!$assignee_list) {
+      //   $errors[] = $this->newInvalidError(
+      //     pht('User "%s" is not a valid user.',
+      //     $new));
+      // }
+    }
+    return $errors;
+  }
+
+}
diff --git a/src/applications/repository/xaction/PhabricatorRepositoryIdentityTransactionType.php b/src/applications/repository/xaction/PhabricatorRepositoryIdentityTransactionType.php
new file mode 100644
--- /dev/null
+++ b/src/applications/repository/xaction/PhabricatorRepositoryIdentityTransactionType.php
@@ -0,0 +1,4 @@
+<?php
+
+abstract class PhabricatorRepositoryIdentityTransactionType
+  extends PhabricatorModularTransactionType {}