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
@@ -431,6 +431,7 @@
     'DifferentialReleephRequestFieldSpecification' => 'applications/releeph/differential/DifferentialReleephRequestFieldSpecification.php',
     'DifferentialRemarkupRule' => 'applications/differential/remarkup/DifferentialRemarkupRule.php',
     'DifferentialReplyHandler' => 'applications/differential/mail/DifferentialReplyHandler.php',
+    'DifferentialRepositoryField' => 'applications/differential/customfield/DifferentialRepositoryField.php',
     'DifferentialRepositoryFieldSpecification' => 'applications/differential/field/specification/DifferentialRepositoryFieldSpecification.php',
     'DifferentialRepositoryLookup' => 'applications/differential/query/DifferentialRepositoryLookup.php',
     'DifferentialResultsTableView' => 'applications/differential/view/DifferentialResultsTableView.php',
@@ -2967,6 +2968,7 @@
     'DifferentialReleephRequestFieldSpecification' => 'DifferentialFieldSpecification',
     'DifferentialRemarkupRule' => 'PhabricatorRemarkupRuleObject',
     'DifferentialReplyHandler' => 'PhabricatorMailReplyHandler',
+    'DifferentialRepositoryField' => 'DifferentialCoreCustomField',
     'DifferentialRepositoryFieldSpecification' => 'DifferentialFieldSpecification',
     'DifferentialRepositoryLookup' => 'Phobject',
     'DifferentialResultsTableView' => 'AphrontView',
diff --git a/src/applications/differential/customfield/DifferentialRepositoryField.php b/src/applications/differential/customfield/DifferentialRepositoryField.php
new file mode 100644
--- /dev/null
+++ b/src/applications/differential/customfield/DifferentialRepositoryField.php
@@ -0,0 +1,128 @@
+<?php
+
+final class DifferentialRepositoryField
+  extends DifferentialCoreCustomField {
+
+  public function getFieldKey() {
+    return 'differential:repository';
+  }
+
+  public function getFieldName() {
+    return pht('Repository');
+  }
+
+  public function getFieldDescription() {
+    return pht('Associates a revision with a repository.');
+  }
+
+  protected function readValueFromRevision(
+    DifferentialRevision $revision) {
+    return $revision->getRepositoryPHID();
+  }
+
+  protected function writeValueToRevision(
+    DifferentialRevision $revision,
+    $value) {
+    $revision->setRepositoryPHID($value);
+  }
+
+  public function readValueFromRequest(AphrontRequest $request) {
+    $phids = $request->getArr($this->getFieldKey());
+    $first = head($phids);
+    $this->setValue(coalesce($first, null));
+  }
+
+  public function getRequiredHandlePHIDsForEdit() {
+    $phids = array();
+    if ($this->getValue()) {
+      $phids[] = $this->getValue();
+    }
+    return $phids;
+  }
+
+  public function renderEditControl(array $handles) {
+
+    if ($this->getValue()) {
+      $control_value = array_select_keys($handles, array($this->getValue()));
+    } else {
+      $control_value = array();
+    }
+
+    return id(new AphrontFormTokenizerControl())
+      ->setName($this->getFieldKey())
+      ->setDatasource('/typeahead/common/repositories/')
+      ->setValue($control_value)
+      ->setError($this->getFieldError())
+      ->setLabel($this->getFieldName())
+      ->setLimit(1);
+  }
+
+  public function getApplicationTransactionRequiredHandlePHIDs(
+    PhabricatorApplicationTransaction $xaction) {
+
+    $old = $xaction->getOldValue();
+    $new = $xaction->getNewValue();
+
+    $phids = array();
+    if ($old) {
+      $phids[] = $old;
+    }
+    if ($new) {
+      $phids[] = $new;
+    }
+
+    return $phids;
+  }
+
+  public function getApplicationTransactionTitle(
+    PhabricatorApplicationTransaction $xaction) {
+    $author_phid = $xaction->getAuthorPHID();
+    $old = $xaction->getOldValue();
+    $new = $xaction->getNewValue();
+
+    if ($old && $new) {
+      return pht(
+        '%s changed the repository for this revision from %s to %s.',
+        $xaction->renderHandleLink($author_phid),
+        $xaction->renderHandleLink($old),
+        $xaction->renderHandleLink($new));
+    } else if ($new) {
+      return pht(
+        '%s set the repository for this revision to %s.',
+        $xaction->renderHandleLink($author_phid),
+        $xaction->renderHandleLink($new));
+    } else {
+      return pht(
+        '%s removed %s as the repository for this revision.',
+        $xaction->renderHandleLink($author_phid),
+        $xaction->renderHandleLink($old));
+    }
+
+  }
+
+  public function getApplicationTransactionTitleForFeed(
+    PhabricatorApplicationTransaction $xaction,
+    PhabricatorFeedStory $story) {
+
+    $object_phid = $xaction->getObjectPHID();
+    $author_phid = $xaction->getAuthorPHID();
+    $old = $xaction->getOldValue();
+    $new = $xaction->getNewValue();
+
+    if ($old) {
+      return pht(
+        '%s updated the repository for %s from %s to %s.',
+        $xaction->renderHandleLink($author_phid),
+        $xaction->renderHandleLink($object_phid),
+        $xaction->renderHandleLink($old),
+        $xaction->renderHandleLink($new));
+    } else {
+      return pht(
+        '%s set the repository for %s to %s.',
+        $xaction->renderHandleLink($author_phid),
+        $xaction->renderHandleLink($object_phid),
+        $xaction->renderHandleLink($new));
+    }
+  }
+
+}
diff --git a/src/applications/differential/customfield/DifferentialSummaryField.php b/src/applications/differential/customfield/DifferentialSummaryField.php
--- a/src/applications/differential/customfield/DifferentialSummaryField.php
+++ b/src/applications/differential/customfield/DifferentialSummaryField.php
@@ -30,7 +30,7 @@
     $this->setValue($request->getStr($this->getFieldKey()));
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new PhabricatorRemarkupControl())
       ->setName($this->getFieldKey())
       ->setValue($this->getValue())
diff --git a/src/applications/differential/customfield/DifferentialTestPlanField.php b/src/applications/differential/customfield/DifferentialTestPlanField.php
--- a/src/applications/differential/customfield/DifferentialTestPlanField.php
+++ b/src/applications/differential/customfield/DifferentialTestPlanField.php
@@ -44,7 +44,7 @@
     $this->setValue($request->getStr($this->getFieldKey()));
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new PhabricatorRemarkupControl())
       ->setName($this->getFieldKey())
       ->setValue($this->getValue())
diff --git a/src/applications/differential/customfield/DifferentialTitleField.php b/src/applications/differential/customfield/DifferentialTitleField.php
--- a/src/applications/differential/customfield/DifferentialTitleField.php
+++ b/src/applications/differential/customfield/DifferentialTitleField.php
@@ -38,7 +38,7 @@
     return true;
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new AphrontFormTextAreaControl())
       ->setHeight(AphrontFormTextAreaControl::HEIGHT_VERY_SHORT)
       ->setName($this->getFieldKey())
diff --git a/src/applications/differential/storage/DifferentialRevision.php b/src/applications/differential/storage/DifferentialRevision.php
--- a/src/applications/differential/storage/DifferentialRevision.php
+++ b/src/applications/differential/storage/DifferentialRevision.php
@@ -468,6 +468,8 @@
     $fields = array(
       new DifferentialTitleField(),
       new DifferentialSummaryField(),
+      new DifferentialTestPlanField(),
+      new DifferentialRepositoryField(),
     );
 
     return array_fill_keys(
diff --git a/src/applications/maniphest/controller/ManiphestTaskEditController.php b/src/applications/maniphest/controller/ManiphestTaskEditController.php
--- a/src/applications/maniphest/controller/ManiphestTaskEditController.php
+++ b/src/applications/maniphest/controller/ManiphestTaskEditController.php
@@ -157,10 +157,10 @@
     $field_list = PhabricatorCustomField::getObjectFields(
       $task,
       PhabricatorCustomField::ROLE_EDIT);
+    $field_list->setViewer($user);
 
     foreach ($field_list->getFields() as $field) {
       $field->setObject($task);
-      $field->setViewer($user);
     }
 
     $field_list->readFieldsFromStorage($task);
@@ -577,10 +577,7 @@
             ->setDatasource('/typeahead/common/projects/'));
     }
 
-    foreach ($aux_fields as $aux_field) {
-      $aux_control = $aux_field->renderEditControl();
-      $form->appendChild($aux_control);
-    }
+    $field_list->appendFieldsToForm($form);
 
     require_celerity_resource('aphront-error-view-css');
 
diff --git a/src/applications/people/customfield/PhabricatorUserBlurbField.php b/src/applications/people/customfield/PhabricatorUserBlurbField.php
--- a/src/applications/people/customfield/PhabricatorUserBlurbField.php
+++ b/src/applications/people/customfield/PhabricatorUserBlurbField.php
@@ -50,7 +50,7 @@
     $this->value = $request->getStr($this->getFieldKey());
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new PhabricatorRemarkupControl())
       ->setName($this->getFieldKey())
       ->setValue($this->value)
diff --git a/src/applications/people/customfield/PhabricatorUserRealNameField.php b/src/applications/people/customfield/PhabricatorUserRealNameField.php
--- a/src/applications/people/customfield/PhabricatorUserRealNameField.php
+++ b/src/applications/people/customfield/PhabricatorUserRealNameField.php
@@ -53,7 +53,7 @@
     $this->value = $request->getStr($this->getFieldKey());
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new AphrontFormTextControl())
       ->setName($this->getFieldKey())
       ->setValue($this->value)
diff --git a/src/applications/people/customfield/PhabricatorUserTitleField.php b/src/applications/people/customfield/PhabricatorUserTitleField.php
--- a/src/applications/people/customfield/PhabricatorUserTitleField.php
+++ b/src/applications/people/customfield/PhabricatorUserTitleField.php
@@ -50,7 +50,7 @@
     $this->value = $request->getStr($this->getFieldKey());
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new AphrontFormTextControl())
       ->setName($this->getFieldKey())
       ->setValue($this->value)
diff --git a/src/applications/transactions/query/PhabricatorApplicationTransactionQuery.php b/src/applications/transactions/query/PhabricatorApplicationTransactionQuery.php
--- a/src/applications/transactions/query/PhabricatorApplicationTransactionQuery.php
+++ b/src/applications/transactions/query/PhabricatorApplicationTransactionQuery.php
@@ -96,27 +96,6 @@
       }
     }
 
-    if ($this->needHandles) {
-      $phids = array();
-      foreach ($xactions as $xaction) {
-        $phids[$xaction->getPHID()] = $xaction->getRequiredHandlePHIDs();
-      }
-      $handles = array();
-      $merged = array_mergev($phids);
-      if ($merged) {
-        $handles = id(new PhabricatorHandleQuery())
-          ->setViewer($this->getViewer())
-          ->withPHIDs($merged)
-          ->execute();
-      }
-      foreach ($xactions as $xaction) {
-        $xaction->setHandles(
-          array_select_keys(
-            $handles,
-            $phids[$xaction->getPHID()]));
-      }
-    }
-
     return $xactions;
   }
 
@@ -138,6 +117,31 @@
       $xaction->attachObject($objects[$object_phid]);
     }
 
+    // NOTE: We have to do this after loading objects, because the objects
+    // may help determine which handles are required (for example, in the case
+    // of custom fields.
+
+    if ($this->needHandles) {
+      $phids = array();
+      foreach ($xactions as $xaction) {
+        $phids[$xaction->getPHID()] = $xaction->getRequiredHandlePHIDs();
+      }
+      $handles = array();
+      $merged = array_mergev($phids);
+      if ($merged) {
+        $handles = id(new PhabricatorHandleQuery())
+          ->setViewer($this->getViewer())
+          ->withPHIDs($merged)
+          ->execute();
+      }
+      foreach ($xactions as $xaction) {
+        $xaction->setHandles(
+          array_select_keys(
+            $handles,
+            $phids[$xaction->getPHID()]));
+      }
+    }
+
     return $xactions;
   }
 
diff --git a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
--- a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
+++ b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
@@ -148,6 +148,13 @@
 
     $phids[] = array($this->getAuthorPHID());
     switch ($this->getTransactionType()) {
+      case PhabricatorTransactions::TYPE_CUSTOMFIELD:
+        $field = $this->getTransactionCustomField();
+        if ($field) {
+          $phids[] = $field->getApplicationTransactionRequiredHandlePHIDs(
+            $this);
+        }
+        break;
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         $phids[] = $old;
         $phids[] = $new;
diff --git a/src/infrastructure/customfield/field/PhabricatorCustomField.php b/src/infrastructure/customfield/field/PhabricatorCustomField.php
--- a/src/infrastructure/customfield/field/PhabricatorCustomField.php
+++ b/src/infrastructure/customfield/field/PhabricatorCustomField.php
@@ -924,6 +924,15 @@
     return null;
   }
 
+  public function getApplicationTransactionRequiredHandlePHIDs(
+    PhabricatorApplicationTransaction $xaction) {
+    if ($this->proxy) {
+      return $this->proxy->getApplicationTransactionRequiredHandlePHIDs(
+        $xaction);
+    }
+    return array();
+  }
+
 
 /* -(  Edit View  )---------------------------------------------------------- */
 
@@ -953,9 +962,20 @@
   /**
    * @task edit
    */
-  public function renderEditControl() {
+  public function getRequiredHandlePHIDsForEdit() {
+    if ($this->proxy) {
+      return $this->proxy->getRequiredHandlePHIDsForEdit();
+    }
+    return array();
+  }
+
+
+  /**
+   * @task edit
+   */
+  public function renderEditControl(array $handles) {
     if ($this->proxy) {
-      return $this->proxy->renderEditControl();
+      return $this->proxy->renderEditControl($handles);
     }
     throw new PhabricatorCustomFieldImplementationIncompleteException($this);
   }
diff --git a/src/infrastructure/customfield/field/PhabricatorCustomFieldList.php b/src/infrastructure/customfield/field/PhabricatorCustomFieldList.php
--- a/src/infrastructure/customfield/field/PhabricatorCustomFieldList.php
+++ b/src/infrastructure/customfield/field/PhabricatorCustomFieldList.php
@@ -10,6 +10,7 @@
 final class PhabricatorCustomFieldList extends Phobject {
 
   private $fields;
+  private $viewer;
 
   public function __construct(array $fields) {
     assert_instances_of($fields, 'PhabricatorCustomField');
@@ -21,6 +22,7 @@
   }
 
   public function setViewer(PhabricatorUser $viewer) {
+    $this->viewer = $viewer;
     foreach ($this->getFields() as $field) {
       $field->setViewer($viewer);
     }
@@ -75,11 +77,32 @@
   }
 
   public function appendFieldsToForm(AphrontFormView $form) {
+    $enabled = array();
     foreach ($this->fields as $field) {
       if ($field->shouldEnableForRole(PhabricatorCustomField::ROLE_EDIT)) {
-        $form->appendChild($field->renderEditControl());
+        $enabled[] = $field;
       }
     }
+
+    $phids = array();
+    foreach ($enabled as $field_key => $field) {
+      $phids[$field_key] = $field->getRequiredHandlePHIDsForEdit();
+    }
+
+    $all_phids = array_mergev($phids);
+    if ($all_phids) {
+      $handles = id(new PhabricatorHandleQuery())
+        ->setViewer($this->viewer)
+        ->withPHIDs($all_phids)
+        ->execute();
+    } else {
+      $handles = array();
+    }
+
+    foreach ($enabled as $field_key => $field) {
+      $field_handles = array_select_keys($handles, $phids[$field_key]);
+      $form->appendChild($field->renderEditControl($field_handles));
+    }
   }
 
   public function appendFieldsToPropertyList(
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomField.php
@@ -200,7 +200,7 @@
     $this->setFieldValue($value);
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new AphrontFormTextControl())
       ->setName($this->getFieldKey())
       ->setCaption($this->getCaption())
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldBool.php
@@ -72,7 +72,7 @@
           )));
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new AphrontFormCheckboxControl())
       ->setLabel($this->getFieldName())
       ->setCaption($this->getCaption())
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
@@ -36,7 +36,7 @@
     return $this->setFieldValue($value);
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return $this->newDateControl();
   }
 
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldHeader.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldHeader.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldHeader.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldHeader.php
@@ -7,7 +7,7 @@
     return 'header';
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     $header = phutil_tag(
       'div',
       array(
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php
@@ -86,4 +86,75 @@
     return $handles;
   }
 
+  public function getRequiredHandlePHIDsForEdit() {
+    $value = $this->getFieldValue();
+    if ($value) {
+      return $value;
+    } else {
+      return array();
+    }
+  }
+
+  public function getApplicationTransactionRequiredHandlePHIDs(
+    PhabricatorApplicationTransaction $xaction) {
+
+    $old = json_decode($xaction->getOldValue());
+    if (!is_array($old)) {
+      $old = array();
+    }
+
+    $new = json_decode($xaction->getNewValue());
+    if (!is_array($new)) {
+      $new = array();
+    }
+
+    $add = array_diff($new, $old);
+    $rem = array_diff($old, $new);
+
+    return array_merge($add, $rem);
+  }
+
+  public function getApplicationTransactionTitle(
+    PhabricatorApplicationTransaction $xaction) {
+    $author_phid = $xaction->getAuthorPHID();
+
+    $old = json_decode($xaction->getOldValue());
+    if (!is_array($old)) {
+      $old = array();
+    }
+
+    $new = json_decode($xaction->getNewValue());
+    if (!is_array($new)) {
+      $new = array();
+    }
+
+    $add = array_diff($new, $old);
+    $rem = array_diff($old, $new);
+
+    if ($add && !$rem) {
+      return pht(
+        '%s updated %s, added %d: %s.',
+        $xaction->renderHandleLink($author_phid),
+        $this->getFieldName(),
+        new PhutilNumber(count($add)),
+        $xaction->renderHandleList($add));
+    } else if ($rem && !$add) {
+      return pht(
+        '%s updated %s, removed %d: %s.',
+        $xaction->renderHandleLink($author_phid),
+        $this->getFieldName(),
+        new PhutilNumber(count($rem)),
+        $xaction->renderHandleList($rem));
+    } else {
+      return pht(
+        '%s updated %s, added %d: %s; removed %d: %s.',
+        $xaction->renderHandleLink($author_phid),
+        $this->getFieldName(),
+        new PhutilNumber(count($add)),
+        $xaction->renderHandleList($add),
+        new PhutilNumber(count($rem)),
+        $xaction->renderHandleList($rem));
+    }
+  }
+
 }
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
@@ -7,7 +7,7 @@
     return 'remarkup';
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new PhabricatorRemarkupControl())
       ->setLabel($this->getFieldName())
       ->setName($this->getFieldKey())
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php
@@ -64,7 +64,7 @@
     return $this->getFieldConfigValue('options', array());
   }
 
-  public function renderEditControl() {
+  public function renderEditControl(array $handles) {
     return id(new AphrontFormSelectControl())
       ->setLabel($this->getFieldName())
       ->setCaption($this->getCaption())
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldUsers.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldUsers.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldUsers.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldUsers.php
@@ -7,17 +7,12 @@
     return 'users';
   }
 
-  public function renderEditControl() {
-    $handles = array();
+  public function renderEditControl(array $handles) {
     $value = $this->getFieldValue();
     if ($value) {
-
-      // TODO: Surface and batch.
-
-      $handles = id(new PhabricatorHandleQuery())
-        ->setViewer($this->getViewer())
-        ->withPHIDs($value)
-        ->execute();
+      $control_value = array_select_keys($handles, $value);
+    } else {
+      $control_value = array();
     }
 
     $control = id(new AphrontFormTokenizerControl())
@@ -25,7 +20,7 @@
       ->setName($this->getFieldKey())
       ->setDatasource('/typeahead/common/accounts/')
       ->setCaption($this->getCaption())
-      ->setValue($handles);
+      ->setValue($control_value);
 
     $limit = $this->getFieldConfigValue('limit');
     if ($limit) {
@@ -49,18 +44,4 @@
 
     $form->appendChild($control);
   }
-
-
-  public function getApplicationTransactionTitle(
-    PhabricatorApplicationTransaction $xaction) {
-    $author_phid = $xaction->getAuthorPHID();
-
-    // TODO: Show added/removed and render handles. We don't have handle
-    // surfacing or batching yet so this is a bit awkward right now.
-
-    return pht(
-      '%s updated %s.',
-      $xaction->renderHandleLink($author_phid),
-      $this->getFieldName());
-  }
 }