Refactor how Mercurial runs commands that require extensions

Summary:
Currently there are a number of `--config extensions.blah=` sprinkled throughout the Mercurial APIs which aren't pleasant to look at. Additionally it turns out the `rebase` command requires the `rebase` extension which is not turned on by default. Uses of `rebase` should also be including this flag to enable the extension when it's in use.

This adds `ArcanistMercurialAPI::buildMercurialExtensionCommand()` which allows running a Mercurial command that requires an extension just by naming the extension instead of providing the full `--config..` argument.

It can be used e.g.
```lang=php
$api->execxLocalWithExtension(
  'strip',
  'strip --rev %s --',
  $rev);

$api->execxLocalWithExtension(
  'arc-hg',
  'arc-amend --logfile %s',
  $tmp_file);
```
Which produces
```lang=console
$ hg --encoding utf-8 --config 'extensions.strip=' strip --rev 82567759e2d703e1e0497f5f41363de3a1500188 --

$ hg --encoding utf-8 --config 'extensions.arg-hg=/Users/cspeckrun/Source/phacility/arcanist/support/hg/arc-hg.py' arc-amend --logfile /private/var/folders/cg/364w44254v5767ydf_x1tg_80000gn/T/6bwck66ccx0kwskw/89989-5F8JaL
```

Refs T13659

Test Plan: I ran through several scenarios of running `arc diff` and `arc land` with uncommitted changes on non-head commits, while not having the `evolve` extension enabled. Using the `--trace` argument I verified that `rebase`, `strip`, `arc-amend`, and `arc-ls-markers` were all invoked and the corresponding `arc diff` and `arc land` commands succeeded. I also ran `arc land --onto-remote default` while `arc-hg.py` raised an exception for the "remote" case and verified that the error was caught by Arcanist and displayed the error and prevented further execution. I removed the error from `arc-hg.py` and re-ran the command and verified it succeeded.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T13659

Differential Revision: https://secure.phabricator.com/D21697

src/land/engine/ArcanistMercurialLandEngine.php

@@ -1160,8 +1160,9 @@ final class ArcanistMercurialLandEngine
         'prune --rev %s',
         $rev_set);
     } else {
-      $api->execxLocal(
-        '--config extensions.strip= strip --rev %s',
+      $api->execxLocalWithExtension(
+        'strip',
+        'strip --rev %s',
         $rev_set);
     }
   }

src/repository/api/ArcanistMercurialAPI.php

@@ -5,6 +5,13 @@
  */
 final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
 
+  /**
+   * Mercurial deceptively indicates that the default encoding is UTF-8 however
+   * however the actual default appears to be "something else", at least on
+   * Windows systems. Force all mercurial commands to use UTF-8 encoding.
+   */
+  const ROOT_HG_COMMAND = 'hg --encoding utf-8 ';
+
   private $branch;
   private $localCommitInfo;
   private $rawDiffCache = array();
@@ -13,28 +20,24 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
   private $featureFutures = array();
 
   protected function buildLocalFuture(array $argv) {
-    $env = $this->getMercurialEnvironmentVariables();
+    $argv[0] = self::ROOT_HG_COMMAND.$argv[0];
 
-    // Mercurial deceptively indicates that the default encoding is UTF-8
-    // however the actual default appears to be "something else", at least on
-    // Windows systems. Force all mercurial commands to use UTF-8 encoding.
-    $argv[0] = 'hg --encoding utf-8 '.$argv[0];
-
-    $future = newv('ExecFuture', $argv)
-      ->setEnv($env)
-      ->setCWD($this->getPath());
-
-    return $future;
+    return $this->newConfiguredFuture(newv('ExecFuture', $argv));
   }
 
   public function newPassthru($pattern /* , ... */) {
     $args = func_get_args();
+    $args[0] = self::ROOT_HG_COMMAND.$args[0];
+
+    return $this->newConfiguredFuture(newv('PhutilExecPassthru', $args));
+  }
+
+  private function newConfiguredFuture(PhutilExecutableFuture $future) {
+    $args = func_get_args();
 
     $env = $this->getMercurialEnvironmentVariables();
 
-    $args[0] = 'hg '.$args[0];
-
-    return newv('PhutilExecPassthru', $args)
+    return $future
       ->setEnv($env)
       ->setCWD($this->getPath());
   }
@@ -730,14 +733,10 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
       'log --template %s --rev . --',
       '{node}');
 
-    $argv = array();
-    foreach ($this->getMercurialExtensionArguments() as $arg) {
-      $argv[] = $arg;
-    }
-    $argv[] = 'arc-amend';
-    $argv[] = '--logfile';
-    $argv[] = $tmp_file;
-    $this->execxLocal('%Ls', $argv);
+    $this->execxLocalWithExtension(
+      'arc-hg',
+      'arc-amend --logfile %s',
+      $tmp_file);
 
     list($new_commit) = $this->execxLocal(
       'log --rev tip --template %s --',
@@ -753,13 +752,20 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
         $rebase_args[] = $child;
       }
 
-      $this->execxLocal('rebase %Ls --', $rebase_args);
+      $this->execxLocalWithExtension(
+        'rebase',
+        'rebase %Ls --',
+        $rebase_args);
     } catch (CommandException $ex) {
-      $this->execxLocal('rebase --abort --');
+      $this->execxLocalWithExtension(
+        'rebase',
+        'rebase --abort --');
       throw $ex;
     }
 
-    $this->execxLocal('--config extensions.strip= strip --rev %s --',
+    $this->execxLocalWithExtension(
+      'strip',
+      'strip --rev %s --',
       $current);
   }
 
@@ -1034,6 +1040,115 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     return $this->executeMercurialFeatureTest($feature, true);
   }
 
+  /**
+   * Returns the necessary flag for using a Mercurial extension. This will
+   * enable Mercurial built-in extensions and the "arc-hg" extension that is
+   * included with Arcanist. This will not enable other extensions, e.g.
+   * "evolve".
+   *
+   * @param string  The name of the extension to enable.
+   * @return string  A new command pattern that includes the necessary flags to
+   *                 enable the specified extension.
+   */
+  private function getMercurialExtensionFlag($extension) {
+    switch ($extension) {
+      case 'arc-hg':
+        $path = phutil_get_library_root('arcanist');
+        $path = dirname($path);
+        $path = $path.'/support/hg/arc-hg.py';
+        $ext_config = 'extensions.arg-hg='.$path;
+        break;
+      case 'rebase':
+        $ext_config = 'extensions.rebase=';
+        break;
+      case 'shelve':
+        $ext_config = 'extensions.shelve=';
+        break;
+      case 'strip':
+        $ext_config = 'extensions.strip=';
+        break;
+      default:
+        throw new Exception(
+          pht('Unknown Mercurial Extension: "%s".', $extension));
+    }
+
+    return csprintf('--config %s', $ext_config);
+  }
+
+  /**
+   * Produces the arguments that should be passed to Mercurial command
+   * execution that enables a desired extension.
+   *
+   * @param string  The name of the extension to enable.
+   * @param string  The command pattern that will be run with the extension
+   *                enabled.
+   * @param array   Parameters for the command pattern argument.
+   * @return array  An array where the first item is a Mercurial command
+   *                pattern that includes the necessary flag for enabling the
+   *                desired extension, and all remaining items are parameters
+   *                to that command pattern.
+   */
+  private function buildMercurialExtensionCommand(
+    $extension,
+    $pattern /* , ... */) {
+
+    $args = func_get_args();
+
+    $pattern_args = array_slice($args, 2);
+
+    $ext_flag = $this->getMercurialExtensionFlag($extension);
+
+    $full_cmd = $ext_flag.' '.$pattern;
+
+    $args = array_merge(
+      array($full_cmd),
+      $pattern_args);
+
+    return $args;
+  }
+
+  public function execxLocalWithExtension(
+    $extension,
+    $pattern /* , ... */) {
+
+    $args = func_get_args();
+    $extended_args = call_user_func_array(
+      array($this, 'buildMercurialExtensionCommand'),
+      $args);
+
+    return call_user_func_array(
+      array($this, 'execxLocal'),
+      $extended_args);
+  }
+
+  public function execFutureLocalWithExtension(
+    $extension,
+    $pattern /* , ... */) {
+
+    $args = func_get_args();
+    $extended_args = call_user_func_array(
+      array($this, 'buildMercurialExtensionCommand'),
+      $args);
+
+    return call_user_func_array(
+      array($this, 'execFutureLocal'),
+      $extended_args);
+  }
+
+  public function execPassthruWithExtension(
+    $extension,
+    $pattern /* , ... */) {
+
+    $args = func_get_args();
+    $extended_args = call_user_func_array(
+      array($this, 'buildMercurialExtensionCommand'),
+      $args);
+
+    return call_user_func_array(
+      array($this, 'execPassthru'),
+      $extended_args);
+  }
+
   private function executeMercurialFeatureTest($feature, $resolve) {
     if (array_key_exists($feature, $this->featureResults)) {
       return $this->featureResults[$feature];
@@ -1059,8 +1174,9 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
   private function newMercurialFeatureFuture($feature) {
     switch ($feature) {
       case 'shelve':
-        return $this->execFutureLocal(
-          '--config extensions.shelve= shelve --help --');
+        return $this->execFutureLocalWithExtension(
+          'shelve',
+          'shelve --help --');
       case 'evolve':
         return $this->execFutureLocal('prune --help --');
       default:
@@ -1094,17 +1210,6 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     return new ArcanistMercurialRepositoryRemoteQuery();
   }
 
-  public function getMercurialExtensionArguments() {
-    $path = phutil_get_library_root('arcanist');
-    $path = dirname($path);
-    $path = $path.'/support/hg/arc-hg.py';
-
-    return array(
-      '--config',
-      'extensions.arc-hg='.$path,
-    );
-  }
-
   protected function newNormalizedURI($uri) {
     return new ArcanistRepositoryURINormalizer(
       ArcanistRepositoryURINormalizer::TYPE_MERCURIAL,

src/repository/marker/ArcanistMercurialRepositoryMarkerQuery.php

@@ -19,12 +19,6 @@ final class ArcanistMercurialRepositoryMarkerQuery
     // to provide a command which works like "git for-each-ref" locally and
     // "git ls-remote" when given a remote.
 
-    $argv = array();
-    foreach ($api->getMercurialExtensionArguments() as $arg) {
-      $argv[] = $arg;
-    }
-    $argv[] = 'arc-ls-markers';
-
     // NOTE: In remote mode, we're using passthru and a tempfile on this
     // because it's a remote command and may prompt the user to provide
     // credentials interactively. In local mode, we can just read stdout.
@@ -33,20 +27,17 @@ final class ArcanistMercurialRepositoryMarkerQuery
       $tmpfile = new TempFile();
       Filesystem::remove($tmpfile);
 
+      $argv = array();
       $argv[] = '--output';
       $argv[] = phutil_string_cast($tmpfile);
-    }
-
-    $argv[] = '--';
-
-    if ($remote !== null) {
+      $argv[] = '--';
       $argv[] = $remote->getRemoteName();
-    }
 
-    if ($remote !== null) {
-      $passthru = $api->newPassthru('%Ls', $argv);
+      $err = $api->execPassthruWithExtension(
+        'arc-hg',
+        'arc-ls-markers %Ls',
+        $argv);
 
-      $err = $passthru->execute();
       if ($err) {
         throw new Exception(
           pht(
@@ -57,8 +48,10 @@ final class ArcanistMercurialRepositoryMarkerQuery
       $raw_data = Filesystem::readFile($tmpfile);
       unset($tmpfile);
     } else {
-      $future = $api->newFuture('%Ls', $argv);
-      list($raw_data) = $future->resolve();
+      $future = $api->execFutureLocalWithExtension(
+        'arc-hg',
+        'arc-ls-markers --');
+      list($err, $raw_data) = $future->resolve();
     }
 
     $items = phutil_json_decode($raw_data);

src/repository/state/ArcanistMercurialLocalState.php

@@ -160,8 +160,9 @@ final class ArcanistMercurialLocalState
       'arc-%s',
       Filesystem::readRandomCharacters(12));
 
-    $api->execxLocal(
-      '--config extensions.shelve= shelve --unknown --name %s --',
+    $api->execxLocalWithExtension(
+      'shelve',
+      'shelve --unknown --name %s --',
       $stash_ref);
 
     $log->writeStatus(
@@ -179,16 +180,18 @@ final class ArcanistMercurialLocalState
       pht('UNSHELVE'),
       pht('Restoring uncommitted changes to working copy.'));
 
-    $api->execxLocal(
-      '--config extensions.shelve= unshelve --keep --name %s --',
+    $api->execxLocalWithExtension(
+      'shelve',
+      'unshelve --keep --name %s --',
       $stash_ref);
   }
 
   protected function discardStash($stash_ref) {
     $api = $this->getRepositoryAPI();
 
-    $api->execxLocal(
-      '--config extensions.shelve= shelve --delete %s --',
+    $api->execxLocalWithExtension(
+      'shelve',
+      'shelve --delete %s --',
       $stash_ref);
   }