When arc has sent target branch data up after D14736, use it in the UI and "Land Revision"

Summary:
Ref T9952. Ref T3462. After D14736, if we have information about the target/"onto" branch, use it in the UI:

  - Show "feature (branched from master)" instead of "feature".
  - Default "Land Revision" to hit the correct branch.

Test Plan:
  - Branched from `test` with branch tracking.
  - Diffed.
  - Saw "feature (branched from test)" in UI.
  - Saw "test" fill as default in "Land Revision", despite the repository having a different default branch.

{F1020587}

{F1020588}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T3462, T9952

Differential Revision: https://secure.phabricator.com/D14737

src/applications/differential/controller/DifferentialRevisionOperationController.php

@@ -30,7 +30,7 @@ final class DifferentialRevisionOperationController
     $diff = $revision->getActiveDiff();
     $repository = $revision->getRepository();
 
-    $default_ref = $this->loadDefaultRef($repository);
+    $default_ref = $this->loadDefaultRef($repository, $diff);
 
     if ($default_ref) {
       $v_ref = array($default_ref->getPHID());
@@ -133,8 +133,10 @@ final class DifferentialRevisionOperationController
     );
   }
 
-  private function loadDefaultRef(PhabricatorRepository $repository) {
-    $default_name = $this->getDefaultRefName($repository);
+  private function loadDefaultRef(
+    PhabricatorRepository $repository,
+    DifferentialDiff $diff) {
+    $default_name = $this->getDefaultRefName($repository, $diff);
 
     if (!strlen($default_name)) {
       return null;
@@ -145,7 +147,15 @@ final class DifferentialRevisionOperationController
       ->executeOne();
   }
 
-  private function getDefaultRefName(PhabricatorRepository $repository) {
+  private function getDefaultRefName(
+    PhabricatorRepository $repository,
+    DifferentialDiff $diff) {
+
+    $onto = $diff->loadTargetBranch();
+    if ($onto !== null) {
+      return $onto;
+    }
+
     return $repository->getDefaultBranch();
   }
 

src/applications/differential/customfield/DifferentialBranchField.php

@@ -44,7 +44,15 @@ final class DifferentialBranchField
     } else if (strlen($bookmark)) {
       return pht('%s (bookmark)', $bookmark);
     } else if (strlen($branch)) {
+      $onto = $diff->loadTargetBranch();
+      if (strlen($onto)) {
+        return pht(
+          '%s (branched from %s)',
+          $branch,
+          $onto);
+      } else {
         return $branch;
+      }
     } else {
       return null;
     }

src/applications/differential/storage/DifferentialDiff.php

@@ -489,6 +489,49 @@ final class DifferentialDiff
     return 'refs/tags/phabricator/diff/'.$this->getID();
   }
 
+  public function loadTargetBranch() {
+    // TODO: This is sketchy, but just eat the query cost until this can get
+    // cleaned up.
+
+    // For now, we're only returning a target if there's exactly one and it's
+    // a branch, since we don't support landing to more esoteric targets like
+    // tags yet.
+
+    $property = id(new DifferentialDiffProperty())->loadOneWhere(
+      'diffID = %d AND name = %s',
+      $this->getID(),
+      'arc:onto');
+    if (!$property) {
+      return null;
+    }
+
+    $data = $property->getData();
+
+    if (!$data) {
+      return null;
+    }
+
+    if (!is_array($data)) {
+      return null;
+    }
+
+    if (count($data) != 1) {
+      return null;
+    }
+
+    $onto = head($data);
+    if (!is_array($onto)) {
+      return null;
+    }
+
+    $type = idx($onto, 'type');
+    if ($type != 'branch') {
+      return null;
+    }
+
+    return idx($onto, 'name');
+  }
+
 
 /* -(  PhabricatorApplicationTransactionInterface  )------------------------- */