diff --git a/src/workingcopy/ArcanistGitWorkingCopy.php b/src/workingcopy/ArcanistGitWorkingCopy.php
new file mode 100644
--- /dev/null
+++ b/src/workingcopy/ArcanistGitWorkingCopy.php
@@ -0,0 +1,22 @@
+<?php
+
+final class ArcanistGitWorkingCopy
+  extends ArcanistWorkingCopy {
+
+  public function getMetadataDirectory() {
+    return $this->getPath('.git');
+  }
+
+  protected function newWorkingCopyFromDirectories(
+    $working_directory,
+    $ancestor_directory) {
+
+    if (!Filesystem::pathExits($ancestor_directory.'/.git')) {
+      return null;
+    }
+
+    return new self();
+  }
+
+}
+
diff --git a/src/workingcopy/ArcanistMercurialWorkingCopy.php b/src/workingcopy/ArcanistMercurialWorkingCopy.php
new file mode 100644
--- /dev/null
+++ b/src/workingcopy/ArcanistMercurialWorkingCopy.php
@@ -0,0 +1,22 @@
+<?php
+
+final class ArcanistMercurialWorkingCopy
+  extends ArcanistWorkingCopy {
+
+  public function getMetadataDirectory() {
+    return $this->getPath('.hg');
+  }
+
+  protected function newWorkingCopyFromDirectories(
+    $working_directory,
+    $ancestor_directory) {
+
+    if (!Filesystem::pathExits($ancestor_directory.'/.hg')) {
+      return null;
+    }
+
+    return new self();
+  }
+
+}
+
diff --git a/src/workingcopy/ArcanistSubversionWorkingCopy.php b/src/workingcopy/ArcanistSubversionWorkingCopy.php
new file mode 100644
--- /dev/null
+++ b/src/workingcopy/ArcanistSubversionWorkingCopy.php
@@ -0,0 +1,51 @@
+<?php
+
+final class ArcanistSubversionWorkingCopy
+  extends ArcanistWorkingCopy {
+
+  public function getProjectConfigurationFilePath() {
+    // In Subversion, we allow ".arcconfig" to appear at any level of the
+    // filesystem between the working directory and the working copy root.
+
+    // We allow this because Subversion repositories are hierarchical and
+    // may have a "projects/xyz/" directory which is meaningfully an entirely
+    // different project from "projects/abc/".
+
+    // You can checkout "projects/" and have the ".svn/" directory appear
+    // there, then change into "abc/" and expect "arc" to operate within the
+    // context of the "abc/" project.
+
+    $paths = Filesystem::walkToRoot($this->getWorkingDirectory());
+    $root = $this->getPath();
+    foreach ($paths as $path) {
+      if (!Filesystem::isDescendant($path, $root)) {
+        break;
+      }
+
+      $candidate = $path.'/.arcconfig';
+      if (Filesystem::pathExists($candidate)) {
+        return $candidate;
+      }
+    }
+
+    return parent::getProjectConfigurationFilePath();
+  }
+
+  public function getMetadataDirectory() {
+    return $this->getPath('.svn');
+  }
+
+  protected function newWorkingCopyFromDirectories(
+    $working_directory,
+    $ancestor_directory) {
+
+    if (!Filesystem::pathExits($ancestor_directory.'/.svn')) {
+      return null;
+    }
+
+    return id(new self());
+  }
+
+
+}
+
diff --git a/src/workingcopy/ArcanistWorkingCopy.php b/src/workingcopy/ArcanistWorkingCopy.php
new file mode 100644
--- /dev/null
+++ b/src/workingcopy/ArcanistWorkingCopy.php
@@ -0,0 +1,95 @@
+<?php
+
+abstract class ArcanistWorkingCopy
+  extends Phobject {
+
+  private $path;
+  private $workingDirectory;
+
+  public static function newFromWorkingDirectory($path) {
+    $working_types = id(new PhutilClassMapQuery())
+      ->setParentClass(__CLASS__)
+      ->execute();
+
+    // Find the outermost directory which is under version control. We go from
+    // the top because:
+    //
+    //   - This gives us a more reasonable behavior if you embed one repository
+    //     inside another repository.
+    //   - This handles old Subversion working copies correctly. Before
+    //     SVN 1.7, Subversion put a ".svn/" directory in every subdirectory.
+
+    $paths = Filesystem::walkToRoot($path);
+    $paths = array_reverse($paths);
+    foreach ($paths as $path_key => $ancestor_path) {
+      foreach ($working_types as $working_type) {
+
+        $working_copy = $working_type->newWorkingCopyFromDirectories(
+          $path,
+          $ancestor_path);
+        if (!$working_copy) {
+          continue;
+        }
+
+        $working_copy->path = $ancestor_path;
+        $working_copy->workingDirectory = $path;
+
+        return $working_copy;
+      }
+    }
+
+    return null;
+  }
+
+  abstract protected function newWorkingCopyFromDirectories(
+    $working_directory,
+    $ancestor_directory);
+
+  final public function getPath($to_file = null) {
+    return Filesystem::concatenatePaths(
+      array(
+        $this->path,
+        $to_file,
+      ));
+  }
+
+  final public function getWorkingDirectory() {
+    return $this->workingDirectory;
+  }
+
+  public function getProjectConfigurationFilePath() {
+    return $this->getPath('.arcconfig');
+  }
+
+  public function getLocalConfigurationFilePath() {
+    if ($this->hasMetadataDirectory()) {
+      return $this->getMetadataPath('arc/config');
+    }
+
+    return null;
+  }
+
+  public function getMetadataDirectory() {
+    return null;
+  }
+
+  final public function hasMetadataDirectory() {
+    return ($this->getMetadataDirectory() !== null);
+  }
+
+  final public function getMetadataPath($to_file = null) {
+    if (!$this->hasMetadataDirectory()) {
+      throw new Exception(
+        pht(
+          'This working copy has no metadata directory, so you can not '.
+          'resolve metadata paths within it.'));
+    }
+
+    return Filesystem::concatenatePaths(
+      array(
+        $this->getMetadataDirectory(),
+        $to_file,
+      ));
+  }
+
+}
diff --git a/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php b/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
deleted file mode 100644
--- a/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
+++ /dev/null
@@ -1,342 +0,0 @@
-<?php
-
-/**
- * Interfaces with basic information about the working copy.
- *
- * @task config
- */
-final class ArcanistWorkingCopyIdentity extends Phobject {
-
-  private $projectConfig;
-  private $projectRoot;
-  private $localConfig = array();
-  private $localMetaDir;
-  private $vcsType;
-  private $vcsRoot;
-
-  public static function newDummyWorkingCopy() {
-    return self::newFromPathWithConfig('/', array());
-  }
-
-  public static function newFromPath($path) {
-    return self::newFromPathWithConfig($path, null);
-  }
-
-  /**
-   * Locate all the information we need about a directory which we presume
-   * to be a working copy. Particularly, we want to discover:
-   *
-   *   - Is the directory inside a working copy (hg, git, svn)?
-   *   - If so, what is the root of the working copy?
-   *   - Is there a `.arcconfig` file?
-   *
-   * This is complicated, mostly because Subversion has special rules. In
-   * particular:
-   *
-   *   - Until 1.7, Subversion put a `.svn/` directory inside //every//
-   *     directory in a working copy. After 1.7, it //only// puts one at the
-   *     root.
-   *   - We allow `.arcconfig` to appear anywhere in a Subversion working copy,
-   *     and use the one closest to the directory.
-   *   - Although we may use a `.arcconfig` from a subdirectory, we store
-   *     metadata in the root's `.svn/`, because it's the only one guaranteed
-   *     to exist.
-   *
-   * Users also do these kinds of things in the wild:
-   *
-   *   - Put working copies inside other working copies.
-   *   - Put working copies inside `.git/` directories.
-   *   - Create `.arcconfig` files at `/.arcconfig`, `/home/.arcconfig`, etc.
-   *
-   * This method attempts to be robust against all sorts of possible
-   * misconfiguration.
-   *
-   * @param string    Path to load information for, usually the current working
-   *                  directory (unless running unit tests).
-   * @param map|null  Pass `null` to locate and load a `.arcconfig` file if one
-   *                  exists. Pass a map to use it to set configuration.
-   * @return ArcanistWorkingCopyIdentity Constructed working copy identity.
-   */
-  private static function newFromPathWithConfig($path, $config) {
-    $project_root = null;
-    $vcs_root = null;
-    $vcs_type = null;
-
-    // First, find the outermost directory which is a Git, Mercurial or
-    // Subversion repository, if one exists. We go from the top because this
-    // makes it easier to identify the root of old SVN working copies (which
-    // have a ".svn/" directory inside every directory in the working copy) and
-    // gives us the right result if you have a Git repository inside a
-    // Subversion repository or something equally ridiculous.
-
-    $paths = Filesystem::walkToRoot($path);
-    $config_paths = array();
-    $paths = array_reverse($paths);
-    foreach ($paths as $path_key => $parent_path) {
-      $try = array(
-        'git' => $parent_path.'/.git',
-        'hg'  => $parent_path.'/.hg',
-        'svn' => $parent_path.'/.svn',
-      );
-
-      foreach ($try as $vcs => $try_dir) {
-        if (!Filesystem::pathExists($try_dir)) {
-          continue;
-        }
-
-        // NOTE: We're distinguishing between the `$project_root` and the
-        // `$vcs_root` because they may not be the same in Subversion. Normally,
-        // they are identical. However, in Subversion, the `$vcs_root` is the
-        // base directory of the working copy (the directory which has the
-        // `.svn/` directory, after SVN 1.7), while the `$project_root` might
-        // be any subdirectory of the `$vcs_root`: it's the the directory
-        // closest to the current directory which contains a `.arcconfig`.
-
-        $project_root = $parent_path;
-        $vcs_root = $parent_path;
-        $vcs_type = $vcs;
-        if ($vcs == 'svn') {
-          // For Subversion, we'll look for a ".arcconfig" file here or in
-          // any subdirectory, starting at the deepest subdirectory.
-          $config_paths = array_slice($paths, $path_key);
-          $config_paths = array_reverse($config_paths);
-        } else {
-          // For Git and Mercurial, we'll only look for ".arcconfig" right here.
-          $config_paths = array($parent_path);
-        }
-        break;
-      }
-    }
-
-    $console = PhutilConsole::getConsole();
-
-    $looked_in = array();
-    foreach ($config_paths as $config_path) {
-      $config_file = $config_path.'/.arcconfig';
-      $looked_in[] = $config_file;
-      if (Filesystem::pathExists($config_file)) {
-        // We always need to examine the filesystem to look for `.arcconfig`
-        // so we can set the project root correctly. We might or might not
-        // actually read the file: if the caller passed in configuration data,
-        // we'll ignore the actual file contents.
-        $project_root = $config_path;
-        if ($config === null) {
-          $console->writeLog(
-            "%s\n",
-            pht(
-              'Working Copy: Reading %s from "%s".',
-              '.arcconfig',
-              $config_file));
-          $config_data = Filesystem::readFile($config_file);
-          $config = self::parseRawConfigFile($config_data, $config_file);
-        }
-        break;
-      }
-    }
-
-    if ($config === null) {
-      if ($looked_in) {
-        $console->writeLog(
-          "%s\n",
-          pht(
-            'Working Copy: Unable to find %s in any of these locations: %s.',
-            '.arcconfig',
-            implode(', ', $looked_in)));
-      } else {
-        $console->writeLog(
-          "%s\n",
-          pht(
-            'Working Copy: No candidate locations for %s from '.
-            'this working directory.',
-            '.arcconfig'));
-      }
-      $config = array();
-    }
-
-    if ($project_root === null) {
-      // We aren't in a working directory at all. This is fine if we're
-      // running a command like "arc help". If we're running something that
-      // requires a working directory, an exception will be raised a little
-      // later on.
-      $console->writeLog(
-        "%s\n",
-        pht('Working Copy: Path "%s" is not in any working copy.', $path));
-      return new ArcanistWorkingCopyIdentity($path, $config);
-    }
-
-    $console->writeLog(
-      "%s\n",
-      pht(
-        'Working Copy: Path "%s" is part of `%s` working copy "%s".',
-        $path,
-        $vcs_type,
-        $vcs_root));
-
-    $console->writeLog(
-      "%s\n",
-      pht(
-        'Working Copy: Project root is at "%s".',
-        $project_root));
-
-    $identity = new ArcanistWorkingCopyIdentity($project_root, $config);
-    $identity->localMetaDir = $vcs_root.'/.'.$vcs_type;
-    $identity->localConfig = $identity->readLocalArcConfig();
-    $identity->vcsType = $vcs_type;
-    $identity->vcsRoot = $vcs_root;
-
-    return $identity;
-  }
-
-  public static function newFromRootAndConfigFile(
-    $root,
-    $config_raw,
-    $from_where) {
-
-    if ($config_raw === null) {
-      $config = array();
-    } else {
-      $config = self::parseRawConfigFile($config_raw, $from_where);
-    }
-
-    return self::newFromPathWithConfig($root, $config);
-  }
-
-  private static function parseRawConfigFile($raw_config, $from_where) {
-    try {
-      return phutil_json_decode($raw_config);
-    } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
-        pht("Unable to parse '%s' file '%s'.", '.arcconfig', $from_where),
-        $ex);
-    }
-  }
-
-  private function __construct($root, array $config) {
-    $this->projectRoot = $root;
-    $this->projectConfig = $config;
-  }
-
-  public function getProjectRoot() {
-    return $this->projectRoot;
-  }
-
-  public function getProjectPath($to_file) {
-    return $this->projectRoot.'/'.$to_file;
-  }
-
-  public function getVCSType() {
-    return $this->vcsType;
-  }
-
-  public function getVCSRoot() {
-    return $this->vcsRoot;
-  }
-
-
-/* -(  Config  )------------------------------------------------------------- */
-
-  public function readProjectConfig() {
-    return $this->projectConfig;
-  }
-
-  /**
-   * Read a configuration directive from project configuration. This reads ONLY
-   * permanent project configuration (i.e., ".arcconfig"), not other
-   * configuration sources. See @{method:getConfigFromAnySource} to read from
-   * user configuration.
-   *
-   * @param key   Key to read.
-   * @param wild  Default value if key is not found.
-   * @return wild Value, or default value if not found.
-   *
-   * @task config
-   */
-  public function getProjectConfig($key, $default = null) {
-    $settings = new ArcanistSettings();
-
-    $pval = idx($this->projectConfig, $key);
-
-    // Test for older names in the per-project config only, since
-    // they've only been used there.
-    if ($pval === null) {
-      $legacy = $settings->getLegacyName($key);
-      if ($legacy) {
-        $pval = $this->getProjectConfig($legacy);
-      }
-    }
-
-    if ($pval === null) {
-      $pval = $default;
-    } else {
-      $pval = $settings->willReadValue($key, $pval);
-    }
-
-    return $pval;
-  }
-
-  /**
-   * Read a configuration directive from local configuration. This
-   * reads ONLY the per-working copy configuration,
-   * i.e. .(git|hg|svn)/arc/config, and not other configuration
-   * sources. See @{method:getConfigFromAnySource} to read from any
-   * config source or @{method:getProjectConfig} to read permanent
-   * project-level config.
-   *
-   * @task config
-   */
-  public function getLocalConfig($key, $default = null) {
-    return idx($this->localConfig, $key, $default);
-  }
-
-  public function readLocalArcConfig() {
-    if (strlen($this->localMetaDir)) {
-      $local_path = Filesystem::resolvePath('arc/config', $this->localMetaDir);
-
-      $console = PhutilConsole::getConsole();
-
-      if (Filesystem::pathExists($local_path)) {
-        $console->writeLog(
-          "%s\n",
-          pht(
-            'Config: Reading local configuration file "%s"...',
-            $local_path));
-
-        try {
-          $json = Filesystem::readFile($local_path);
-          return phutil_json_decode($json);
-        } catch (PhutilJSONParserException $ex) {
-          throw new PhutilProxyException(
-            pht("Failed to parse '%s' as JSON.", $local_path),
-            $ex);
-        }
-      } else {
-        $console->writeLog(
-          "%s\n",
-          pht(
-            'Config: Did not find local configuration at "%s".',
-            $local_path));
-      }
-    }
-
-    return array();
-  }
-
-  public function writeLocalArcConfig(array $config) {
-    $json_encoder = new PhutilJSON();
-    $json = $json_encoder->encodeFormatted($config);
-
-    $dir = $this->localMetaDir;
-    if (!strlen($dir)) {
-      throw new Exception(pht('No working copy to write config into!'));
-    }
-
-    $local_dir = $dir.DIRECTORY_SEPARATOR.'arc';
-    if (!Filesystem::pathExists($local_dir)) {
-      Filesystem::createDirectory($local_dir, 0755);
-    }
-
-    $config_file = $local_dir.DIRECTORY_SEPARATOR.'config';
-    Filesystem::writeFile($config_file, $json);
-  }
-
-}
diff --git a/support/ArcanistRuntime.php b/support/ArcanistRuntime.php
--- a/support/ArcanistRuntime.php
+++ b/support/ArcanistRuntime.php
@@ -202,15 +202,14 @@
   }
 
   private function loadConfiguration(PhutilArgumentParser $args) {
-    $configuration_manager = new ArcanistConfigurationManager();
+    $engine = new ArcanistConfigurationEngine();
 
-    $cwd = getcwd();
-    $working_copy = ArcanistWorkingCopyIdentity::newFromPath($cwd);
-    $configuration_manager->setWorkingCopyIdentity($working_copy);
-
-    $configuration_manager->applyRuntimeArcConfig($args);
+    $working_copy = ArcanistWorkingCopyIdentity::newFromPath(getcwd());
+    if ($working_copy) {
+      $engine->setWorkingCopy($working_copy);
+    }
 
-    return $configuration_manager;
+    return $engine->newConfigurationSourceList();
   }
 
   private function loadLibraries(