diff --git a/src/applications/repository/customfield/PhabricatorCommitBranchesField.php b/src/applications/repository/customfield/PhabricatorCommitBranchesField.php
--- a/src/applications/repository/customfield/PhabricatorCommitBranchesField.php
+++ b/src/applications/repository/customfield/PhabricatorCommitBranchesField.php
@@ -7,13 +7,14 @@
     return 'diffusion:branches';
   }
 
-  public function shouldAppearInApplicationTransactions() {
+  public function shouldAppearInTransactionMail() {
     return true;
   }
 
-  public function buildApplicationTransactionMailBody(
-    PhabricatorApplicationTransaction $xaction,
-    PhabricatorMetaMTAMailBody $body) {
+  public function updateTransactionMailBody(
+    PhabricatorMetaMTAMailBody $body,
+    PhabricatorApplicationTransactionEditor $editor,
+    array $xactions) {
 
     $params = array(
       'contains' => $this->getObject()->getCommitIdentifier(),
diff --git a/src/applications/repository/customfield/PhabricatorCommitTagsField.php b/src/applications/repository/customfield/PhabricatorCommitTagsField.php
--- a/src/applications/repository/customfield/PhabricatorCommitTagsField.php
+++ b/src/applications/repository/customfield/PhabricatorCommitTagsField.php
@@ -7,13 +7,14 @@
     return 'diffusion:tags';
   }
 
-  public function shouldAppearInApplicationTransactions() {
+  public function shouldAppearInTransactionMail() {
     return true;
   }
 
-  public function buildApplicationTransactionMailBody(
-    PhabricatorApplicationTransaction $xaction,
-    PhabricatorMetaMTAMailBody $body) {
+  public function updateTransactionMailBody(
+    PhabricatorMetaMTAMailBody $body,
+    PhabricatorApplicationTransactionEditor $editor,
+    array $xactions) {
 
     $params = array(
       'commit' => $this->getObject()->getCommitIdentifier(),
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
@@ -1055,22 +1055,6 @@
     return false;
   }
 
-  /**
-   * TODO: this is only used by Diffusion right now and everything is completely
-   * faked since Diffusion doesn't use ApplicationTransactions yet. This should
-   * get fleshed out as we have more use cases.
-   *
-   * @task appxaction
-   */
-  public function buildApplicationTransactionMailBody(
-    PhabricatorApplicationTransaction $xaction,
-    PhabricatorMetaMTAMailBody $body) {
-    if ($this->proxy) {
-      return $this->proxy->buildApplicationTransactionMailBody($xaction, $body);
-    }
-    return;
-  }
-
 
 /* -(  Transaction Mail  )--------------------------------------------------- */