Clean up hg --debug branches calls

Summary: Ref T1493. Consolidate these a bit; they might need some more magic once we do `--noupdate` checkouts. Mostly just trying to clean up and centralize this code a bit.

Test Plan: Viewed and `bin/repository discover`'d Mercurial repos with and without any branches.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1493

Differential Revision: https://secure.phabricator.com/D7480

src/__phutil_library_map__.php

@@ -496,6 +496,7 @@ phutil_register_library_map(array(
     'DiffusionLintDetailsController' => 'applications/diffusion/controller/DiffusionLintDetailsController.php',
     'DiffusionLintSaveRunner' => 'applications/diffusion/DiffusionLintSaveRunner.php',
     'DiffusionLowLevelGitRefQuery' => 'applications/diffusion/query/lowlevel/DiffusionLowLevelGitRefQuery.php',
+    'DiffusionLowLevelMercurialBranchesQuery' => 'applications/diffusion/query/lowlevel/DiffusionLowLevelMercurialBranchesQuery.php',
     'DiffusionLowLevelQuery' => 'applications/diffusion/query/lowlevel/DiffusionLowLevelQuery.php',
     'DiffusionMercurialCommitParentsQuery' => 'applications/diffusion/query/parents/DiffusionMercurialCommitParentsQuery.php',
     'DiffusionMercurialExpandShortNameQuery' => 'applications/diffusion/query/expandshortname/DiffusionMercurialExpandShortNameQuery.php',
@@ -2701,6 +2702,7 @@ phutil_register_library_map(array(
     'DiffusionLintController' => 'DiffusionController',
     'DiffusionLintDetailsController' => 'DiffusionController',
     'DiffusionLowLevelGitRefQuery' => 'DiffusionLowLevelQuery',
+    'DiffusionLowLevelMercurialBranchesQuery' => 'DiffusionLowLevelQuery',
     'DiffusionLowLevelQuery' => 'Phobject',
     'DiffusionMercurialCommitParentsQuery' => 'DiffusionCommitParentsQuery',
     'DiffusionMercurialExpandShortNameQuery' => 'DiffusionExpandShortNameQuery',

src/applications/diffusion/conduit/ConduitAPI_diffusion_branchquery_Method.php

@@ -65,17 +65,9 @@ final class ConduitAPI_diffusion_branchquery_Method
     $offset = $request->getValue('offset');
     $limit = $request->getValue('limit');
 
-    list($stdout) = $repository->execxLocalCommand(
-      '--debug branches');
-    $branch_info = ArcanistMercurialParser::parseMercurialBranches($stdout);
-
-    $branches = array();
-    foreach ($branch_info as $name => $info) {
-      $branch = new DiffusionBranchInformation();
-      $branch->setName($name);
-      $branch->setHeadCommitIdentifier($info['rev']);
-      $branches[] = $branch->toDictionary();
-    }
+    $branches = id(new DiffusionLowLevelMercurialBranchesQuery())
+      ->setRepository($repository)
+      ->execute();
 
     if ($offset) {
       $branches = array_slice($branches, $offset);
@@ -85,6 +77,6 @@ final class ConduitAPI_diffusion_branchquery_Method
       $branches = array_slice($branches, 0, $limit);
     }
 
-    return $branches;
+    return mpull($branches, 'toDictionary');
   }
 }

src/applications/diffusion/query/lowlevel/DiffusionLowLevelMercurialBranchesQuery.php

@@ -0,0 +1,28 @@
+<?php
+
+/**
+ * Execute and parse a low-level Mercurial branches query using `hg branches`.
+ */
+final class DiffusionLowLevelMercurialBranchesQuery
+  extends DiffusionLowLevelQuery {
+
+  protected function executeQuery() {
+    $repository = $this->getRepository();
+
+    // NOTE: `--debug` gives us 40-character hashes.
+    list($stdout) = $repository->execxLocalCommand(
+      '--debug branches');
+
+    $branches = array();
+
+    $lines = ArcanistMercurialParser::parseMercurialBranches($stdout);
+    foreach ($lines as $name => $spec) {
+      $branches[] = id(new DiffusionBranchInformation())
+        ->setName($name)
+        ->setHeadCommitIdentifier($spec['rev']);
+    }
+
+    return $branches;
+  }
+
+}

src/applications/repository/daemon/PhabricatorRepositoryPullLocalDaemon.php

@@ -743,15 +743,12 @@ final class PhabricatorRepositoryPullLocalDaemon
 
 
   private function executeHgDiscover(PhabricatorRepository $repository) {
-    // NOTE: "--debug" gives us 40-character hashes.
-    list($stdout) = $repository->execxLocalCommand('--debug branches');
 
-    if (!trim($stdout)) {
-      // No branches; likely a newly initialized repository.
-      return false;
-    }
+    $branches = id(new DiffusionLowLevelMercurialBranchesQuery())
+      ->setRepository($repository)
+      ->execute();
+    $branches = mpull($branches, 'getHeadCommitIdentifier', 'getName');
 
-    $branches = ArcanistMercurialParser::parseMercurialBranches($stdout);
     $got_something = false;
     foreach ($branches as $name => $branch) {
       $commit = $branch['rev'];