Index: src/__phutil_library_map__.php
===================================================================
--- src/__phutil_library_map__.php
+++ src/__phutil_library_map__.php
@@ -49,9 +49,13 @@
     'ArcanistAbstractMethodBodyXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistAbstractMethodBodyXHPASTLinterRuleTestCase.php',
     'ArcanistAbstractPrivateMethodXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistAbstractPrivateMethodXHPASTLinterRule.php',
     'ArcanistAbstractPrivateMethodXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistAbstractPrivateMethodXHPASTLinterRuleTestCase.php',
+    'ArcanistAlias' => 'toolset/ArcanistAlias.php',
+    'ArcanistAliasEffect' => 'toolset/ArcanistAliasEffect.php',
+    'ArcanistAliasEngine' => 'toolset/ArcanistAliasEngine.php',
     'ArcanistAliasFunctionXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistAliasFunctionXHPASTLinterRule.php',
     'ArcanistAliasFunctionXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistAliasFunctionXHPASTLinterRuleTestCase.php',
     'ArcanistAliasWorkflow' => 'toolset/workflow/ArcanistAliasWorkflow.php',
+    'ArcanistAliasesConfigOption' => 'config/option/ArcanistAliasesConfigOption.php',
     'ArcanistAmendWorkflow' => 'workflow/ArcanistAmendWorkflow.php',
     'ArcanistAnoidWorkflow' => 'workflow/ArcanistAnoidWorkflow.php',
     'ArcanistArcConfigurationEngineExtension' => 'config/arc/ArcanistArcConfigurationEngineExtension.php',
@@ -303,6 +307,7 @@
     'ArcanistLintersWorkflow' => 'workflow/ArcanistLintersWorkflow.php',
     'ArcanistListAssignmentXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistListAssignmentXHPASTLinterRule.php',
     'ArcanistListAssignmentXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistListAssignmentXHPASTLinterRuleTestCase.php',
+    'ArcanistListConfigOption' => 'config/option/ArcanistListConfigOption.php',
     'ArcanistListWorkflow' => 'workflow/ArcanistListWorkflow.php',
     'ArcanistLocalConfigurationSource' => 'config/source/ArcanistLocalConfigurationSource.php',
     'ArcanistLogicalOperatorsXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistLogicalOperatorsXHPASTLinterRule.php',
@@ -491,6 +496,8 @@
     'ArcanistWhichWorkflow' => 'workflow/ArcanistWhichWorkflow.php',
     'ArcanistWildConfigOption' => 'config/option/ArcanistWildConfigOption.php',
     'ArcanistWorkflow' => 'toolset/ArcanistWorkflow.php',
+    'ArcanistWorkflowArgument' => 'toolset/ArcanistWorkflowArgument.php',
+    'ArcanistWorkflowInformation' => 'toolset/ArcanistWorkflowInformation.php',
     'ArcanistWorkingCopy' => 'workingcopy/ArcanistWorkingCopy.php',
     'ArcanistWorkingCopyConfigurationSource' => 'config/source/ArcanistWorkingCopyConfigurationSource.php',
     'ArcanistWorkingCopyStateRef' => 'ref/ArcanistWorkingCopyStateRef.php',
@@ -1145,9 +1152,13 @@
     'ArcanistAbstractMethodBodyXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
     'ArcanistAbstractPrivateMethodXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
     'ArcanistAbstractPrivateMethodXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
+    'ArcanistAlias' => 'Phobject',
+    'ArcanistAliasEffect' => 'Phobject',
+    'ArcanistAliasEngine' => 'Phobject',
     'ArcanistAliasFunctionXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
     'ArcanistAliasFunctionXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
     'ArcanistAliasWorkflow' => 'ArcanistWorkflow',
+    'ArcanistAliasesConfigOption' => 'ArcanistListConfigOption',
     'ArcanistAmendWorkflow' => 'ArcanistWorkflow',
     'ArcanistAnoidWorkflow' => 'ArcanistWorkflow',
     'ArcanistArcConfigurationEngineExtension' => 'ArcanistConfigurationEngineExtension',
@@ -1399,6 +1410,7 @@
     'ArcanistLintersWorkflow' => 'ArcanistWorkflow',
     'ArcanistListAssignmentXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
     'ArcanistListAssignmentXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
+    'ArcanistListConfigOption' => 'ArcanistConfigOption',
     'ArcanistListWorkflow' => 'ArcanistWorkflow',
     'ArcanistLocalConfigurationSource' => 'ArcanistWorkingCopyConfigurationSource',
     'ArcanistLogicalOperatorsXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
@@ -1587,6 +1599,8 @@
     'ArcanistWhichWorkflow' => 'ArcanistWorkflow',
     'ArcanistWildConfigOption' => 'ArcanistConfigOption',
     'ArcanistWorkflow' => 'Phobject',
+    'ArcanistWorkflowArgument' => 'Phobject',
+    'ArcanistWorkflowInformation' => 'Phobject',
     'ArcanistWorkingCopy' => 'Phobject',
     'ArcanistWorkingCopyConfigurationSource' => 'ArcanistFilesystemConfigurationSource',
     'ArcanistWorkingCopyStateRef' => 'ArcanistRef',
Index: src/config/ArcanistConfigurationSourceList.php
===================================================================
--- src/config/ArcanistConfigurationSourceList.php
+++ src/config/ArcanistConfigurationSourceList.php
@@ -15,16 +15,80 @@
     return $this->sources;
   }
 
+  private function getSourcesWithScopes($scopes) {
+    if ($scopes !== null) {
+      $scopes = array_fuse($scopes);
+    }
+
+    $results = array();
+    foreach ($this->getSources() as $source) {
+      if ($scopes !== null) {
+        $scope = $source->getConfigurationSourceScope();
+        if ($scope === null) {
+          continue;
+        }
+        if (!isset($scopes[$scope])) {
+          continue;
+        }
+      }
+
+      $results[] = $source;
+    }
+
+    return $results;
+  }
+
+  public function getWritableSourceFromScope($scope) {
+    $sources = $this->getSourcesWithScopes(array($scope));
+
+    $writable = array();
+    foreach ($sources as $source) {
+      if (!$source->isWritableConfigurationSource()) {
+        continue;
+      }
+
+      $writable[] = $source;
+    }
+
+    if (!$writable) {
+      throw new Exception(
+        pht(
+          'Unable to write configuration: there is no writable configuration '.
+          'source in the "%s" scope.',
+          $scope));
+    }
+
+    if (count($writable) > 1) {
+      throw new Exception(
+        pht(
+          'Unable to write configuration: more than one writable source '.
+          'exists in the "%s" scope.',
+          $scope));
+    }
+
+    return head($writable);
+  }
+
   public function getConfig($key) {
     $option = $this->getConfigOption($key);
     $values = $this->getStorageValueList($key);
     return $option->getValueFromStorageValueList($values);
   }
 
+  public function getConfigFromScopes($key, array $scopes) {
+    $option = $this->getConfigOption($key);
+    $values = $this->getStorageValueListFromScopes($key, $scopes);
+    return $option->getValueFromStorageValueList($values);
+  }
+
   public function getStorageValueList($key) {
+    return $this->getStorageValueListFromScopes($key, null);
+  }
+
+  private function getStorageValueListFromScopes($key, $scopes) {
     $values = array();
 
-    foreach ($this->getSources() as $source) {
+    foreach ($this->getSourcesWithScopes($scopes) as $source) {
       if ($source->hasValueForKey($key)) {
         $value = $source->getValueForKey($key);
         $values[] = new ArcanistConfigurationSourceValue(
@@ -113,7 +177,13 @@
             $source,
             $raw_value);
         } catch (Exception $ex) {
-          throw $ex;
+          throw new PhutilProxyException(
+            pht(
+              'Configuration value ("%s") defined in source "%s" is not '.
+              'valid.',
+              $key,
+              $source->getSourceDisplayName()),
+            $ex);
         }
       }
     }
Index: src/config/arc/ArcanistArcConfigurationEngineExtension.php
===================================================================
--- src/config/arc/ArcanistArcConfigurationEngineExtension.php
+++ src/config/arc/ArcanistArcConfigurationEngineExtension.php
@@ -5,6 +5,8 @@
 
   const EXTENSIONKEY = 'arc';
 
+  const KEY_ALIASES = 'aliases';
+
   public function newConfigurationOptions() {
     // TOOLSETS: Restore "load", and maybe this other stuff.
 
@@ -49,12 +51,6 @@
         'example' => 'false',
       ),
 
-      'aliases' => array(
-        'type' => 'aliases',
-        'help' => pht(
-          'Configured command aliases. Use "arc alias" to define aliases.'),
-      ),
-
       'history.immutable' => array(
         'type' => 'bool',
         'legacy' => 'immutable_history',
@@ -160,6 +156,14 @@
           array(
             'https://phabricator.mycompany.com/',
           )),
+      id(new ArcanistAliasesConfigOption())
+        ->setKey(self::KEY_ALIASES)
+        ->setDefaultValue(array())
+        ->setSummary(pht('List of command aliases.'))
+        ->setHelp(
+          pht(
+            'Configured command aliases. Use the "alias" workflow to define '.
+            'aliases.')),
     );
   }
 
Index: src/config/option/ArcanistAliasesConfigOption.php
===================================================================
--- /dev/null
+++ src/config/option/ArcanistAliasesConfigOption.php
@@ -0,0 +1,36 @@
+<?php
+
+final class ArcanistAliasesConfigOption
+  extends ArcanistListConfigOption {
+
+  public function getType() {
+    return 'list<alias>';
+  }
+
+  public function getValueFromStorageValue($value) {
+    if (!is_array($value)) {
+      throw new Exception(pht('Expected a list or dictionary!'));
+    }
+
+    $aliases = array();
+    foreach ($value as $key => $spec) {
+      $aliases[] = ArcanistAlias::newFromConfig($key, $spec);
+    }
+
+    return $aliases;
+  }
+
+  protected function didReadStorageValueList(array $list) {
+    assert_instances_of($list, 'ArcanistConfigurationSourceValue');
+    return mpull($list, 'getValue');
+  }
+
+  public function getDisplayValueFromValue($value) {
+    return pht('Use the "alias" workflow to review aliases.');
+  }
+
+  public function getStorageValueFromValue($value) {
+    return mpull($value, 'getStorageDictionary');
+  }
+
+}
Index: src/config/option/ArcanistConfigOption.php
===================================================================
--- src/config/option/ArcanistConfigOption.php
+++ src/config/option/ArcanistConfigOption.php
@@ -67,9 +67,17 @@
   abstract public function getType();
 
   abstract public function getValueFromStorageValueList(array $list);
-  abstract public function getStorageValueFromStringValue($value);
   abstract public function getValueFromStorageValue($value);
   abstract public function getDisplayValueFromValue($value);
+  abstract public function getStorageValueFromValue($value);
+
+  public function getStorageValueFromStringValue($value) {
+    throw new Exception(
+      pht(
+        'This configuration option ("%s") does not support runtime definition '.
+        'with "--config".',
+        $this->getKey()));
+  }
 
   protected function getStorageValueFromSourceValue(
     ArcanistConfigurationSourceValue $source_value) {
@@ -84,5 +92,9 @@
     return $value;
   }
 
+  public function writeValue(ArcanistConfigurationSource $source, $value) {
+    $value = $this->getStorageValueFromValue($value);
+    $source->setStorageValueForKey($this->getKey(), $value);
+  }
 
 }
Index: src/config/option/ArcanistListConfigOption.php
===================================================================
--- /dev/null
+++ src/config/option/ArcanistListConfigOption.php
@@ -0,0 +1,32 @@
+<?php
+
+abstract class ArcanistListConfigOption
+  extends ArcanistConfigOption {
+
+  public function getValueFromStorageValueList(array $list) {
+    assert_instances_of($list, 'ArcanistConfigurationSourceValue');
+
+    $result_list = array();
+    foreach ($list as $source_value) {
+      $source = $source_value->getConfigurationSource();
+      $storage_value = $this->getStorageValueFromSourceValue($source_value);
+
+      $items = $this->getValueFromStorageValue($storage_value);
+      foreach ($items as $item) {
+        $result_list[] = new ArcanistConfigurationSourceValue(
+          $source,
+          $item);
+      }
+    }
+
+    $result_list = $this->didReadStorageValueList($result_list);
+
+    return $result_list;
+  }
+
+  protected function didReadStorageValueList(array $list) {
+    assert_instances_of($list, 'ArcanistConfigurationSourceValue');
+    return mpull($list, 'getValue');
+  }
+
+}
Index: src/config/option/ArcanistStringConfigOption.php
===================================================================
--- src/config/option/ArcanistStringConfigOption.php
+++ src/config/option/ArcanistStringConfigOption.php
@@ -15,4 +15,8 @@
     return $value;
   }
 
+  public function getStorageValueFromValue($value) {
+    return $value;
+  }
+
 }
Index: src/config/source/ArcanistConfigurationSource.php
===================================================================
--- src/config/source/ArcanistConfigurationSource.php
+++ src/config/source/ArcanistConfigurationSource.php
@@ -3,15 +3,25 @@
 abstract class ArcanistConfigurationSource
   extends Phobject {
 
+  const SCOPE_USER = 'user';
+
   abstract public function getSourceDisplayName();
   abstract public function getAllKeys();
   abstract public function hasValueForKey($key);
   abstract public function getValueForKey($key);
 
+  public function getConfigurationSourceScope() {
+    return null;
+  }
+
   public function isStringSource() {
     return false;
   }
 
+  public function isWritableConfigurationSource() {
+    return false;
+  }
+
   public function didReadUnknownOption($key) {
     // TOOLSETS: Standardize this kind of messaging? On ArcanistRuntime?
 
Index: src/config/source/ArcanistDictionaryConfigurationSource.php
===================================================================
--- src/config/source/ArcanistDictionaryConfigurationSource.php
+++ src/config/source/ArcanistDictionaryConfigurationSource.php
@@ -29,4 +29,16 @@
     return $this->values[$key];
   }
 
+  public function setStorageValueForKey($key, $value) {
+    $this->values[$key] = $value;
+
+    $this->writeToStorage($this->values);
+
+    return $this;
+  }
+
+  protected function writeToStorage($values) {
+    throw new PhutilMethodNotImplementedException();
+  }
+
 }
\ No newline at end of file
Index: src/config/source/ArcanistFilesystemConfigurationSource.php
===================================================================
--- src/config/source/ArcanistFilesystemConfigurationSource.php
+++ src/config/source/ArcanistFilesystemConfigurationSource.php
@@ -35,4 +35,11 @@
     return $values;
   }
 
+  protected function writeToStorage($values) {
+    $content = id(new PhutilJSON())
+      ->encodeFormatted($values);
+
+    Filesystem::writeFile($this->path, $content);
+  }
+
 }
\ No newline at end of file
Index: src/config/source/ArcanistUserConfigurationSource.php
===================================================================
--- src/config/source/ArcanistUserConfigurationSource.php
+++ src/config/source/ArcanistUserConfigurationSource.php
@@ -7,6 +7,14 @@
     return pht('User Config File');
   }
 
+  public function isWritableConfigurationSource() {
+    return true;
+  }
+
+  public function getConfigurationSourceScope() {
+    return ArcanistConfigurationSource::SCOPE_USER;
+  }
+
   public function didReadFilesystemValues(array $values) {
     // Before toolsets, the "~/.arcrc" file had separate top-level keys for
     // "config", "hosts", and "aliases". Transform this older file format into
Index: src/toolset/ArcanistAlias.php
===================================================================
--- /dev/null
+++ src/toolset/ArcanistAlias.php
@@ -0,0 +1,145 @@
+<?php
+
+final class ArcanistAlias extends Phobject {
+
+  private $toolset;
+  private $trigger;
+  private $command;
+  private $exception;
+  private $configurationSource;
+
+  public static function newFromConfig($key, $value) {
+    $alias = new self();
+
+    // Parse older style aliases which were always for the "arc" toolset.
+    // When we next write these back into the config file, we'll update them
+    // to the modern format.
+
+    // The old format looked like this:
+    //
+    //   {
+    //     "draft": ["diff", "--draft"]
+    //   }
+    //
+    // The new format looks like this:
+    //
+    //   {
+    //     [
+    //       "toolset": "arc",
+    //       "trigger": "draft",
+    //       "command": ["diff", "--draft"]
+    //     ]
+    //   }
+    //
+    // For now, we parse the older format and fill in the toolset as "arc".
+
+    $is_list = false;
+    $is_dict = false;
+    if ($value && is_array($value)) {
+      if (array_keys($value) === range(0, count($value) - 1)) {
+        $is_list = true;
+      } else {
+        $is_dict = true;
+      }
+    }
+
+    if ($is_list) {
+      $alias->trigger = $key;
+      $alias->toolset = 'arc';
+      $alias->command = $value;
+    } else if ($is_dict) {
+      try {
+        PhutilTypeSpec::checkMap(
+          $value,
+          array(
+            'trigger' => 'string',
+            'toolset' => 'string',
+            'command' => 'list<string>',
+          ));
+
+        $alias->trigger = idx($value, 'trigger');
+        $alias->toolset = idx($value, 'toolset');
+        $alias->command = idx($value, 'command');
+      } catch (PhutilTypeCheckException $ex) {
+        $alias->exception = new PhutilProxyException(
+          pht(
+            'Found invalid alias definition (with key "%s").',
+            $key),
+          $ex);
+      }
+    } else {
+      $alias->exception = new Exception(
+        pht(
+          'Expected alias definition (with key "%s") to be a dictionary.',
+          $key));
+    }
+
+    return $alias;
+  }
+
+  public function setToolset($toolset) {
+    $this->toolset = $toolset;
+    return $this;
+  }
+
+  public function getToolset() {
+    return $this->toolset;
+  }
+
+  public function setTrigger($trigger) {
+    $this->trigger = $trigger;
+    return $this;
+  }
+
+  public function getTrigger() {
+    return $this->trigger;
+  }
+
+  public function setCommand(array $command) {
+    $this->command = $command;
+    return $this;
+  }
+
+  public function getCommand() {
+    return $this->command;
+  }
+
+  public function setException(Exception $exception) {
+    $this->exception = $exception;
+    return $this;
+  }
+
+  public function getException() {
+    return $this->exception;
+  }
+
+  public function isShellCommandAlias() {
+    $command = $this->getCommand();
+    if (!$command) {
+      return false;
+    }
+
+    $head = head($command);
+    return preg_match('/^!/', $head);
+  }
+
+  public function getStorageDictionary() {
+    return array(
+      'trigger' => $this->getTrigger(),
+      'toolset' => $this->getToolset(),
+      'command' => $this->getCommand(),
+    );
+  }
+
+  public function setConfigurationSource(
+    ArcanistConfigurationSource $configuration_source) {
+    $this->configurationSource = $configuration_source;
+    return $this;
+  }
+
+  public function getConfigurationSource() {
+    return $this->configurationSource;
+  }
+
+}
+
Index: src/toolset/ArcanistAliasEffect.php
===================================================================
--- /dev/null
+++ src/toolset/ArcanistAliasEffect.php
@@ -0,0 +1,57 @@
+<?php
+
+final class ArcanistAliasEffect
+  extends Phobject {
+
+  private $type;
+  private $command;
+  private $arguments;
+  private $message;
+
+  const EFFECT_MISCONFIGURATION = 'misconfiguration';
+  const EFFECT_SHELL = 'shell';
+  const EFFECT_RESOLUTION = 'resolution';
+  const EFFECT_SUGGEST = 'suggest';
+  const EFFECT_OVERRIDDE = 'override';
+  const EFFECT_ALIAS = 'alias';
+  const EFFECT_NOTFOUND = 'not-found';
+  const EFFECT_CYCLE = 'cycle';
+  const EFFECT_STACK = 'stack';
+
+  public function setType($type) {
+    $this->type = $type;
+    return $this;
+  }
+
+  public function getType() {
+    return $this->type;
+  }
+
+  public function setCommand($command) {
+    $this->command = $command;
+    return $this;
+  }
+
+  public function getCommand() {
+    return $this->command;
+  }
+
+  public function setArguments(array $arguments) {
+    $this->arguments = $arguments;
+    return $this;
+  }
+
+  public function getArguments() {
+    return $this->arguments;
+  }
+
+  public function setMessage($message) {
+    $this->message = $message;
+    return $this;
+  }
+
+  public function getMessage() {
+    return $this->message;
+  }
+
+}
\ No newline at end of file
Index: src/toolset/ArcanistAliasEngine.php
===================================================================
--- /dev/null
+++ src/toolset/ArcanistAliasEngine.php
@@ -0,0 +1,255 @@
+<?php
+
+final class ArcanistAliasEngine
+  extends Phobject {
+
+  private $runtime;
+  private $toolset;
+  private $workflows;
+  private $configurationSourceList;
+
+  public function setRuntime(ArcanistRuntime $runtime) {
+    $this->runtime = $runtime;
+    return $this;
+  }
+
+  public function getRuntime() {
+    return $this->runtime;
+  }
+
+  public function setToolset(ArcanistToolset $toolset) {
+    $this->toolset = $toolset;
+    return $this;
+  }
+
+  public function getToolset() {
+    return $this->toolset;
+  }
+
+  public function setWorkflows(array $workflows) {
+    assert_instances_of($workflows, 'ArcanistWorkflow');
+    $this->workflows = $workflows;
+    return $this;
+  }
+
+  public function getWorkflows() {
+    return $this->workflows;
+  }
+
+  public function setConfigurationSourceList(
+    ArcanistConfigurationSourceList $config) {
+    $this->configurationSourceList = $config;
+    return $this;
+  }
+
+  public function getConfigurationSourceList() {
+    return $this->configurationSourceList;
+  }
+
+  public function resolveAliases(array $argv) {
+    $aliases_key = ArcanistArcConfigurationEngineExtension::KEY_ALIASES;
+    $source_list = $this->getConfigurationSourceList();
+    $aliases = $source_list->getConfig($aliases_key);
+
+    $results = array();
+
+    // Identify aliases which had some kind of format or specification issue
+    // when loading config. We could possibly do this earlier, but it's nice
+    // to handle all the alias stuff in one place.
+
+    foreach ($aliases as $key => $alias) {
+      $exception = $alias->getException();
+
+      if (!$exception) {
+        continue;
+      }
+
+      // This alias is not defined properly, so we're going to ignore it.
+      unset($aliases[$key]);
+
+      $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_CONFIGURATION)
+        ->setMessage(
+          pht(
+            'Configuration source ("%s") defines an invalid alias, which '.
+            'will be ignored: %s',
+            $alias->getConfigurationSource()->getSourceDisplayName()),
+            $exception->getMessage());
+    }
+
+    $command = array_shift($argv);
+
+    $stack = array();
+    return $this->resolveAliasesForCommand(
+      $aliases,
+      $command,
+      $argv,
+      $results,
+      $stack);
+  }
+
+  private function resolveAliasesForCommand(
+    array $aliases,
+    $command,
+    array $argv,
+    array $results,
+    array $stack) {
+
+    $toolset = $this->getToolset();
+    $toolset_key = $toolset->getToolsetKey();
+
+    // If we have a command which resolves to a real workflow, match it and
+    // finish resolution. You can not overwrite a real workflow with an alias.
+
+    $workflows = $this->getWorkflows();
+    if (isset($workflows[$command])) {
+      $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_RESOLUTION)
+        ->setCommand($command)
+        ->setArguments($argv);
+      return $results;
+    }
+
+    // Find all the aliases which match whatever the user typed, like "draft".
+    // We look for aliases in other toolsets, too, so we can provide the user
+    // a hint when they type "phage draft" and mean "arc draft".
+
+    $matches = array();
+    $toolset_matches = array();
+    foreach ($aliases as $alias) {
+      if ($alias->getTrigger() === $command) {
+        $matches[] = $alias;
+        if ($alias->getToolset() == $toolset_key) {
+          $toolset_matches[] = $alias;
+        }
+      }
+    }
+
+    if (!$toolset_matches) {
+
+      // If the user typed "phage draft" and meant "arc draft", give them a
+      // hint that the alias exists somewhere else and they may have specified
+      // the wrong toolset.
+
+      foreach ($matches as $match) {
+        $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_SUGGEST)
+          ->setMessage(
+            pht(
+              'No "%s %s" alias is defined, did you mean "%s %s"?',
+              $toolset_key,
+              $command,
+              $match->getToolset(),
+              $command));
+      }
+
+      // If the user misspells a command (like "arc hlep") and it doesn't match
+      // anything (no alias or workflow), we want to pass it through unmodified
+      // and let the parser try to correct the spelling into a real workflow
+      // later on.
+
+      // However, if the user correctly types a command (like "arc draft") that
+      // resolves at least once (so it hits a valid alias) but does not
+      // ultimately resolve into a valid workflow, we want to treat this as a
+      // hard failure.
+
+      // This could happen if you manually defined a bad alias, or a workflow
+      // you'd previously aliased to was removed, or you stacked aliases and
+      // then deleted one.
+
+      if ($stack) {
+        $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_NOTFOUND)
+          ->setMessage(
+            pht(
+              'Alias resolved to "%s", but this is not a valid workflow or '.
+              'alias name. This alias or workflow might have previously '.
+              'existed and been removed.',
+              $command));
+      } else {
+        $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_RESOLUTION)
+          ->setCommand($command)
+          ->setArguments($argv);
+      }
+
+      return $results;
+    }
+
+    $alias = array_pop($toolset_matches);
+    foreach ($toolset_matches as $ignored_match) {
+      $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_IGNORED)
+        ->setMessage(
+          pht(
+            'Multiple configuration sources define an alias for "%s %s". '.
+            'The definition in "%s" will be ignored.',
+            $toolset_key,
+            $command,
+            $ignored_match->getConfigurationSource()->getSourceDisplayName()));
+    }
+
+    if ($alias->isShellCommandAlias()) {
+      $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_SHELL)
+        ->setMessage(
+          pht(
+            '%s %s -> $ %s',
+            $toolset_key,
+            $command,
+            $alias->getShellCommand()))
+        ->setCommand($command)
+        ->setArgv($argv);
+      return $results;
+    }
+
+    $alias_argv = $alias->getCommand();
+    $alias_command = array_shift($alias_argv);
+
+    if (isset($stack[$alias_command])) {
+
+      $cycle = array_keys($stack);
+      $cycle[] = $alias_command;
+      $cycle = implode(' -> ', $cycle);
+
+      $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_CYCLE)
+        ->setMessage(
+          pht(
+            'Alias definitions form a cycle which can not be resolved: %s.',
+            $cycle));
+
+      return $results;
+    }
+
+    $stack[$alias_command] = true;
+
+    $stack_limit = 16;
+    if (count($stack) >= $stack_limit) {
+      $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_STACK)
+        ->setMessage(
+          pht(
+            'Alias definitions form an unreasonably deep stack. A chain of '.
+            'aliases may not resolve more than %s times.',
+            new PhutilNumber($stack_limit)));
+      return $results;
+    }
+
+    $results[] = $this->newEffect(ArcanistAliasEffect::EFFECT_ALIAS)
+      ->setMessage(
+        pht(
+          '%s %s -> %s %s',
+          $toolset_key,
+          $command,
+          $toolset_key,
+          $alias_command));
+
+    $argv = array_merge($alias_argv, $argv);
+
+    return $this->resolveAliasesForCommand(
+      $aliases,
+      $alias_command,
+      $argv,
+      $results,
+      $stack);
+  }
+
+  protected function newEffect($effect_type) {
+    return id(new ArcanistAliasEffect())
+      ->setType($effect_type);
+  }
+
+}
+
Index: src/toolset/ArcanistWorkflow.php
===================================================================
--- src/toolset/ArcanistWorkflow.php
+++ src/toolset/ArcanistWorkflow.php
@@ -2,6 +2,7 @@
 
 abstract class ArcanistWorkflow extends Phobject {
 
+  private $runtime;
   private $toolset;
   private $arguments;
   private $configurationEngine;
@@ -37,10 +38,48 @@
     return true;
   }
 
+  protected function getWorkflowArguments() {
+    // TOOLSETS: Temporary!
+    return array();
+  }
+
+  protected function getWorkflowInformation() {
+    // TOOLSETS: Temporary!
+    return null;
+  }
+
+
   public function newPhutilWorkflow() {
-    return id(new ArcanistPhutilWorkflow())
+    $arguments = $this->getWorkflowArguments();
+    assert_instances_of($arguments, 'ArcanistWorkflowArgument');
+
+    $specs = mpull($arguments, 'getPhutilSpecification');
+
+    $phutil_workflow = id(new ArcanistPhutilWorkflow())
       ->setName($this->getWorkflowName())
-      ->setWorkflow($this);
+      ->setWorkflow($this)
+      ->setArguments($specs);
+
+    $information = $this->getWorkflowInformation();
+    if ($information) {
+
+      $examples = $information->getExamples();
+      if ($examples) {
+        $examples = implode("\n", $examples);
+        $phutil_workflow->setExamples($examples);
+      }
+
+      $help = $information->getHelp();
+      if (strlen($help)) {
+        // Unwrap linebreaks in the help text so we don't get weird formatting.
+        $help = preg_replace("/(?<=\S)\n(?=\S)/", " ", $help);
+
+        $phutil_workflow->setHelp($help);
+      }
+
+    }
+
+    return $phutil_workflow;
   }
 
   final public function getToolset() {
@@ -52,6 +91,19 @@
     return $this;
   }
 
+  final public function setRuntime(ArcanistRuntime $runtime) {
+    $this->runtime = $runtime;
+    return $this;
+  }
+
+  final public function getRuntime() {
+    return $this->runtime;
+  }
+
+  final public function getConfig($key) {
+    return $this->getConfigurationSourceList()->getConfig($key);
+  }
+
   final public function setConfigurationSourceList(
     ArcanistConfigurationSourceList $config) {
     $this->configurationSourceList = $config;
@@ -99,11 +151,17 @@
     return $err;
   }
 
-  final public function getArgument($key, $default = null) {
-    // TOOLSETS: This is a stub for now.
-    return $default;
+  final public function getArgument($key) {
+    return $this->arguments->getArg($key);
+  }
+
+  final protected function newWorkflowArgument($key) {
+    return id(new ArcanistWorkflowArgument())
+      ->setKey($key);
+  }
 
-    return $this->arguments->getArg($key, $default);
+  final protected function newWorkflowInformation() {
+    return new ArcanistWorkflowInformation();
   }
 
 }
Index: src/toolset/ArcanistWorkflowArgument.php
===================================================================
--- /dev/null
+++ src/toolset/ArcanistWorkflowArgument.php
@@ -0,0 +1,50 @@
+<?php
+
+final class ArcanistWorkflowArgument
+  extends Phobject {
+
+  private $key;
+  private $help;
+  private $wildcard;
+
+  public function setKey($key) {
+    $this->key = $key;
+    return $this;
+  }
+
+  public function getKey() {
+    return $this->key;
+  }
+
+  public function setWildcard($wildcard) {
+    $this->wildcard = $wildcard;
+    return $this;
+  }
+
+  public function getWildcard() {
+    return $this->wildcard;
+  }
+
+  public function getPhutilSpecification() {
+    $spec = array(
+      'name' => $this->getKey(),
+    );
+
+    if ($this->getWildcard()) {
+      $spec['wildcard'] = true;
+    }
+
+    return $spec;
+  }
+
+  public function setHelp($help) {
+    $this->help = $help;
+    return $this;
+  }
+
+  public function getHelp() {
+    return $this->help;
+  }
+
+}
+
Index: src/toolset/ArcanistWorkflowInformation.php
===================================================================
--- /dev/null
+++ src/toolset/ArcanistWorkflowInformation.php
@@ -0,0 +1,28 @@
+<?php
+
+final class ArcanistWorkflowInformation
+  extends Phobject {
+
+  private $help;
+  private $examples = array();
+
+  public function setHelp($help) {
+    $this->help = $help;
+    return $this;
+  }
+
+  public function getHelp() {
+    return $this->help;
+  }
+
+  public function addExample($example) {
+    $this->examples[] = $example;
+    return $this;
+  }
+
+  public function getExamples() {
+    return $this->examples;
+  }
+
+}
+
Index: src/toolset/workflow/ArcanistAliasWorkflow.php
===================================================================
--- src/toolset/workflow/ArcanistAliasWorkflow.php
+++ src/toolset/workflow/ArcanistAliasWorkflow.php
@@ -13,232 +13,186 @@
     return true;
   }
 
-  public function getWorkflowSynopses() {
-    return array(
-      pht('**alias**'),
-      pht('**alias** __command__'),
-      pht('**alias** __command__ __target__ -- [__options__]'),
-    );
-  }
-
-  public function getWorkflowHelp() {
-    return pht(<<<EOTEXT
-Supports: cli
+  public function getWorkflowInformation() {
+    $help = pht(<<<EOTEXT
 Create an alias from __command__ to __target__ (optionally, with __options__).
-For example:
 
-  %s alias fpatch patch -- --force
+Aliases allow you to create shorthands for commands and sets of flags you
+commonly use, like defining "arc draft" as a shorthand for "arc diff --draft".
+
+**Creating Aliases**
+
+You can define "arc draft" as a shorthand for "arc diff --draft" like this:
+
+  $ arc alias draft diff -- --draft
 
-...will create a new 'arc' command, 'arc fpatch', which invokes
-'arc patch --force ...' when run. NOTE: use "--" before specifying
-options!
+Now, when you run "arc draft", the command will function like
+"arc diff --draft".
 
-If you start an alias with "!", the remainder of the alias will be
-invoked as a shell command. For example, if you want to implement
-'arc ls', you can do so like this:
+<bg:yellow> NOTE: </bg> Make sure you use "--" before specifying any flags you
+want to pass to the command! Otherwise, the flags will be interpreted as flags
+to "arc alias".
 
-  %s alias ls '!ls'
+**Listing Aliases**
 
-You can now run "arc ls" and it will behave like "ls". Of course, this
-example is silly and would make your life worse.
+Without any arguments, "arc alias" will list aliases.
 
-You can not overwrite builtins, including 'alias' itself. The builtin
-will always execute, even if it was added after your alias.
+**Removing Aliases**
 
 To remove an alias, run:
 
-  arc alias fpatch
+  $ arc alias <alias-name>
+
+You will be prompted to remove the alias.
+
+**Shell Commands**
+
+If you begin an alias with "!", the remainder of the alias will be invoked as
+a shell command. For example, if you want to implement "arc ls", you can do so
+like this:
+
+  $ arc alias ls '!ls'
+
+When run, "arc ls" will now behave like "ls".
+
+**Multiple Toolsets**
 
-Without any arguments, 'arc alias' will list aliases.
+This workflow supports any toolset, even though the examples in this help text
+use "arc". If you are working with another toolset, use the binary for that
+toolset define aliases for it:
+
+  $ phage alias ...
+
+Aliases are bound to the toolset which was used to define them. If you define
+an "arc draft" alias, that does not also define a "phage draft" alias.
+
+**Builtins**
+
+You can not overwrite the behavior of builtin workflows, including "alias"
+itself, and if you install a new workflow it will take precedence over any
+existing aliases with the same name.
 EOTEXT
-    ,
-    $this->getToolsetName());
+);
+
+    return $this->newWorkflowInformation()
+      ->addExample(pht('**alias**'))
+      ->addExample(pht('**alias** __command__'))
+      ->addExample(pht('**alias** __command__ __target__ -- [__options__]'))
+      ->setHelp($help);
   }
 
-  public function getArguments() {
+  public function getWorkflowArguments() {
     return array(
-      '*' => 'argv',
+      $this->newWorkflowArgument('json')
+        ->setHelp(pht('Output aliases in JSON format.')),
+      $this->newWorkflowArgument('argv')
+        ->setWildcard(true),
     );
   }
 
-  public static function getAliases(
-    ArcanistConfigurationManager $configuration_manager) {
-    $sources = $configuration_manager->getConfigFromAllSources('aliases');
+  public function runWorkflow() {
+    $argv = $this->getArgument('argv');
 
-    $aliases = array();
-    foreach ($sources as $source) {
-      $aliases += $source;
-    }
+    $is_list = false;
+    $is_delete = false;
 
-    return $aliases;
-  }
+    if (!$argv) {
+      $is_list = true;
+    } else if (count($argv) === 1) {
+      $is_delete = true;
+    }
 
-  private function writeAliases(array $aliases) {
-    $config = $this->getConfigurationManager()->readUserConfigurationFile();
-    $config['aliases'] = $aliases;
-    $this->getConfigurationManager()->writeUserConfigurationFile($config);
-  }
+    $is_json = $this->getArgument('json');
+    if ($is_json && !$is_list) {
+      throw new PhutilArgumentUsageException(
+        pht(
+          'The "--json" argument may only be used when listing aliases.'));
+    }
 
-  public function runWorkflow() {
-    $aliases = self::getAliases($this->getConfigurationManager());
+    if ($is_list) {
+      return $this->runListAliases();
+    }
 
-    $argv = $this->getArgument('argv');
-    if (count($argv) == 0) {
-      $this->printAliases($aliases);
-    } else if (count($argv) == 1) {
-      $this->removeAlias($aliases, $argv[0]);
-    } else {
-      $arc_config = $this->getArcanistConfiguration();
-      $alias = $argv[0];
-
-      if ($arc_config->buildWorkflow($alias)) {
-        throw new ArcanistUsageException(
-          pht(
-            'You can not create an alias for "%s" because it is a '.
-            'builtin command. "%s" can only create new commands.',
-            "arc {$alias}",
-            'arc alias'));
-      }
-
-      $new_alias = array_slice($argv, 1);
-
-      $command = implode(' ', $new_alias);
-      if (self::isShellCommandAlias($command)) {
-        echo tsprintf(
-          "%s\n",
-          pht(
-            'Aliased "%s" to shell command "%s".',
-            "arc {$alias}",
-            substr($command, 1)));
-      } else {
-        echo tsprintf(
-          "%s\n",
-          pht(
-            'Aliased "%s" to "%s".',
-            "arc {$alias}",
-            "arc {$command}"));
-      }
-
-      $aliases[$alias] = $new_alias;
-      $this->writeAliases($aliases);
+    if ($is_delete) {
+      return $this->runDeleteAlias($argv[1]);
     }
 
-    return 0;
+    return $this->runCreateAlias($argv);
   }
 
-  public static function isShellCommandAlias($command) {
-    return preg_match('/^!/', $command);
+  private function runListAliases() {
+    // TOOLSETS: Actually list aliases.
+    return 1;
   }
 
-  public static function resolveAliases(
-    $command,
-    ArcanistRuntime $config,
-    array $argv,
-    ArcanistConfigurationManager $configuration_manager) {
+  private function runDeleteAlias($alias) {
+    // TOOLSETS: Actually delete aliases.
+    return 1;
+  }
 
-    $aliases = self::getAliases($configuration_manager);
-    if (!isset($aliases[$command])) {
-      return array(null, $argv);
-    }
+  private function runCreateAlias(array $argv) {
+    $trigger = array_shift($argv);
+    $this->validateAliasTrigger($trigger);
 
-    $new_command = head($aliases[$command]);
+    $alias = id(new ArcanistAlias())
+      ->setToolset($this->getToolsetKey())
+      ->setTrigger($trigger)
+      ->setCommand($argv);
 
-    if (self::isShellCommandAlias($new_command)) {
-      return array($new_command, $argv);
-    }
+    $aliases = $this->readAliasesForWrite();
 
-    $workflow = $config->buildWorkflow($new_command);
-    if (!$workflow) {
-      return array(null, $argv);
-    }
+    // TOOLSETS: Check if the user already has an alias for this trigger, and
+    // prompt them to overwrite it. Needs prompting to work.
 
-    $alias_argv = array_slice($aliases[$command], 1);
-    foreach (array_reverse($alias_argv) as $alias_arg) {
-      if (!in_array($alias_arg, $argv)) {
-        array_unshift($argv, $alias_arg);
-      }
-    }
+    $aliases[] = $alias;
 
-    return array($new_command, $argv);
+    $this->writeAliases($aliases);
+
+    return 0;
   }
 
-  private function printAliases(array $aliases) {
-    if (!$aliases) {
-      echo tsprintf(
-        "%s\n",
-        pht('You have not defined any aliases yet.'));
-      return;
-    }
+  private function validateAliasTrigger($trigger) {
+    $workflows = $this->getRuntime()->getWorkflows();
 
-    $table = id(new PhutilConsoleTable())
-      ->addColumn('input', array('title' => pht('Alias')))
-      ->addColumn('command', array('title' => pht('Command')))
-      ->addColumn('type', array('title' => pht('Type')));
-
-    ksort($aliases);
-
-    foreach ($aliases as $alias => $binding) {
-      $command = implode(' ', $binding);
-      if (self::isShellCommandAlias($command)) {
-        $command = substr($command, 1);
-        $type = pht('Shell Command');
-      } else {
-        $command = "arc {$command}";
-        $type = pht('Arcanist Command');
-      }
-
-      $row = array(
-        'input' => "arc {$alias}",
-        'type' => $type,
-        'command' => $command,
-      );
-
-      $table->addRow($row);
+    if (isset($workflows[$trigger])) {
+      throw new PhutilArgumentUsageException(
+        pht(
+          'You can not define an alias for "%s" because it is a builtin '.
+          'workflow for the current toolset ("%s"). The "alias" workflow '.
+          'can only define new commands as aliases; it can not redefine '.
+          'existing commands to mean something else.',
+          $trigger,
+          $this->getToolsetKey()));
     }
+  }
 
-    $table->draw();
+  private function getEditScope() {
+    return ArcanistConfigurationSource::SCOPE_USER;
   }
 
-  private function removeAlias(array $aliases, $alias) {
-    if (empty($aliases[$alias])) {
-      echo tsprintf(
-        "%s\n",
-        pht('No alias "%s" to remove.', $alias));
-      return;
-    }
+  private function getAliasesConfigKey() {
+    return ArcanistArcConfigurationEngineExtension::KEY_ALIASES;
+  }
 
-    $command = implode(' ', $aliases[$alias]);
+  private function readAliasesForWrite() {
+    $key = $this->getAliasesConfigKey();
+    $scope = $this->getEditScope();
+    $source_list = $this->getConfigurationSourceList();
 
-    if (self::isShellCommandAlias($command)) {
-      echo tsprintf(
-        "%s\n",
-        pht(
-          '"%s" is currently aliased to shell command "%s".',
-          "arc {$alias}",
-          substr($command, 1)));
-    } else {
-      echo tsprintf(
-        "%s\n",
-        pht(
-          '"%s" is currently aliased to "%s".',
-          "arc {$alias}",
-          "arc {$command}"));
-    }
+    return $source_list->getConfigFromScopes($key, array($scope));
+  }
 
+  private function writeAliases(array $aliases) {
+    assert_instances_of($aliases, 'ArcanistAlias');
 
-    $ok = phutil_console_confirm(pht('Delete this alias?'));
-    if (!$ok) {
-      throw new ArcanistUserAbortException();
-    }
+    $key = $this->getAliasesConfigKey();
+    $scope = $this->getEditScope();
 
-    unset($aliases[$alias]);
-    $this->writeAliases($aliases);
+    $source_list = $this->getConfigurationSourceList();
+    $source = $source_list->getWritableSourceFromScope($scope);
+    $option = $source_list->getConfigOption($key);
 
-    echo tsprintf(
-      "%s\n",
-      pht(
-        'Removed alias "%s".',
-        "arc {$alias}"));
+    $option->writeValue($source, $aliases);
   }
 
 }
Index: src/workflow/ArcanistLiberateWorkflow.php
===================================================================
--- src/workflow/ArcanistLiberateWorkflow.php
+++ src/workflow/ArcanistLiberateWorkflow.php
@@ -1,70 +1,32 @@
 <?php
 
-/**
- * Create and update libphutil libraries.
- *
- * This workflow is unusual and involves re-executing 'arc liberate' as a
- * subprocess with `--remap` and `--verify`. This is because there is no way
- * to unload or reload a library, so every process is stuck with the library
- * definition it had when it first loaded. This is normally fine, but
- * problematic in this case because `arc liberate` modifies library definitions.
- */
 final class ArcanistLiberateWorkflow extends ArcanistWorkflow {
 
   public function getWorkflowName() {
     return 'liberate';
   }
 
-  public function getCommandSynopses() {
-    return phutil_console_format(<<<EOTEXT
-      **liberate** [__path__]
-EOTEXT
-      );
-  }
+  public function getWorkflowInformation() {
+    // TOOLSETS: Expand this help.
 
-  public function getCommandHelp() {
-    return phutil_console_format(<<<EOTEXT
-          Supports: libphutil
-          Create or update a libphutil library, generating required metadata
-          files like \__init__.php.
+    $help = pht(<<<EOTEXT
+Create or update an Arcanist library.
 EOTEXT
-      );
+);
+
+    return $this->newWorkflowInformation()
+      ->addExample(pht('**liberate**'))
+      ->addExample(pht('**liberate** [__path__]'))
+      ->setHelp($help);
   }
 
-  public function getArguments() {
+  public function getWorkflowArguments() {
     return array(
-      'all' => array(
-        'help' => pht(
-          'Drop the module cache before liberating. This will completely '.
-          'reanalyze the entire library. Thorough, but slow!'),
-      ),
-      'force-update' => array(
-        'help' => pht(
-          'Force the library map to be updated, even in the presence of '.
-          'lint errors.'),
-      ),
-      'library-name' => array(
-        'param' => 'name',
-        'help' =>
-          pht('Use a flag for library name rather than awaiting user input.'),
-      ),
-      'remap' => array(
-        'hide' => true,
-        'help' => pht(
-          'Internal. Run the remap step of liberation. You do not need to '.
-          'run this unless you are debugging the workflow.'),
-      ),
-      'verify' => array(
-        'hide' => true,
-        'help' => pht(
-          'Internal. Run the verify step of liberation. You do not need to '.
-          'run this unless you are debugging the workflow.'),
-      ),
-      'upgrade' => array(
-        'hide'  => true,
-        'help'  => pht('Experimental. Upgrade library to v2.'),
-      ),
-      '*' => 'argv',
+      $this->newWorkflowArgument('clean')
+        ->setHelp(
+          pht('Perform a clean rebuild, ignoring caches. Thorough, but slow.')),
+      $this->newWorkflowArgument('argv')
+        ->setWildcard(true),
     );
   }
 
@@ -97,9 +59,6 @@
       );
     }
 
-    $is_remap = $this->getArgument('remap');
-    $is_verify = $this->getArgument('verify');
-
     foreach ($paths as $path) {
       $this->liberatePath($path);
     }
@@ -122,19 +81,10 @@
     $version = $this->getLibraryFormatVersion($path);
     switch ($version) {
       case 1:
-        if ($this->getArgument('upgrade')) {
-          return $this->upgradeLibrary($path);
-        }
         throw new ArcanistUsageException(
           pht(
-            "This library is using libphutil v1, which is no ".
-            "longer supported. Run '%s' to upgrade to v2.",
-            'arc liberate --upgrade'));
+            'This very old library is no longer supported.'));
       case 2:
-        if ($this->getArgument('upgrade')) {
-          throw new ArcanistUsageException(
-            pht("Can't upgrade a v2 library!"));
-        }
         return $this->liberateVersion2($path);
       default:
         throw new ArcanistUsageException(
@@ -165,25 +115,10 @@
     return phutil_passthru(
       'php %s %C %s',
       $bin,
-      $this->getArgument('all') ? '--drop-cache' : '',
+      $this->getArgument('clean') ? '--drop-cache' : '',
       $path);
   }
 
-  private function upgradeLibrary($path) {
-    $inits = id(new FileFinder($path))
-      ->withPath('*/__init__.php')
-      ->withType('f')
-      ->find();
-
-    echo pht('Removing %s files...', '__init__.php')."\n";
-    foreach ($inits as $init) {
-      Filesystem::remove($path.'/'.$init);
-    }
-
-    echo pht('Upgrading library to v2...')."\n";
-    $this->liberateVersion2($path);
-  }
-
   private function liberateCreateDirectory($path) {
     if (Filesystem::pathExists($path)) {
       if (!is_dir($path)) {
Index: support/ArcanistRuntime.php
===================================================================
--- support/ArcanistRuntime.php
+++ support/ArcanistRuntime.php
@@ -2,6 +2,8 @@
 
 final class ArcanistRuntime {
 
+  private $workflows;
+
   public function execute(array $argv) {
 
     try {
@@ -81,12 +83,14 @@
     $args->parsePartial($toolset->getToolsetArguments());
 
     $workflows = $this->newWorkflows($toolset);
+    $this->workflows = $workflows;
 
     $phutil_workflows = array();
     foreach ($workflows as $key => $workflow) {
       $phutil_workflows[$key] = $workflow->newPhutilWorkflow();
 
       $workflow
+        ->setRuntime($this)
         ->setConfigurationEngine($config_engine)
         ->setConfigurationSourceList($config);
     }
@@ -104,12 +108,16 @@
       throw new PhutilArgumentUsageException(pht('Choose a workflow!'));
     }
 
-    $result = $this->resolveAliases($workflows, $unconsumed_argv, $config);
-    if (is_int($result)) {
-      return $result;
-    }
+    $alias_effects = id(new ArcanistAliasEngine())
+      ->setRuntime($this)
+      ->setToolset($toolset)
+      ->setWorkflows($workflows)
+      ->setConfigurationSourceList($config)
+      ->resolveAliases($unconsumed_argv);
 
-    $args->setUnconsumedArgumentVector($result);
+    $result_argv = $this->applyAliasEffects($alias_effects, $unconsumed_argv);
+
+    $args->setUnconsumedArgumentVector($result_argv);
 
     return $args->parseWorkflows($phutil_workflows);
   }
@@ -468,70 +476,45 @@
     return $map;
   }
 
-  private function resolveAliases(
-    array $workflows,
-    array $argv,
-    ArcanistConfigurationSourceList $config) {
-
-    return $argv;
+  private function logTrace($label, $message) {
+    echo tsprintf(
+      "**<bg:magenta> %s </bg>** %s\n",
+      $label,
+      $message);
+  }
 
-    $command = head($argv);
+  public function getWorkflows() {
+    return $this->workflows;
+  }
 
-    // If this is a match for a recognized workflow, just return the arguments
-    // unmodified. You aren't allowed to alias over real workflows.
-    if (isset($workflows[$command])) {
-      return $argv;
-    }
+  private function applyAliasEffects(array $effects, array $argv) {
+    assert_instances_of($effects, 'ArcanistAliasEffect');
+
+    $command = null;
+    $arguments = null;
+    foreach ($effects as $effect) {
+      $message = $effect->getMessage();
+
+      if ($message !== null) {
+        fprintf(
+          STDERR,
+          tsprintf(
+            "**<bg:yellow> %s </bg>** %s\n",
+            pht('ALIAS'),
+            $message));
+      }
 
-    $aliases = ArcanistAliasWorkflow::getAliases($config);
-    list($new_command, $new_args) = ArcanistAliasWorkflow::resolveAliases(
-      $command,
-      $this,
-      array_slice($argv, 1),
-      $config);
-
-    // You can't alias something to itself, so if the new command isn't new,
-    // we're all done resolving aliases.
-    if ($new_command === $command) {
-      return $argv;
+      if ($effect->getCommand()) {
+        $command = $effect->getCommand();
+        $arguments = $effect->getArguments();
+      }
     }
 
-    $full_alias = idx($aliases, $command, array());
-    $full_alias = implode(' ', $full_alias);
-
-    // Run shell command aliases.
-    if (ArcanistAliasWorkflow::isShellCommandAlias($new_command)) {
-      fwrite(
-        STDERR,
-        tsprintf(
-          '**<bg:green> %s </bg>** arc %s -> $ %s',
-          pht('ALIAS'),
-          $command,
-          $shell_cmd));
-
-      $shell_cmd = substr($full_alias, 1);
-
-      return phutil_passthru('%C %Ls', $shell_cmd, $args);
+    if ($command !== null) {
+      $argv = array_merge(array($command), $arguments);
     }
 
-    fwrite(
-      STDERR,
-      tsprintf(
-        '**<bg:green> %s </bg>** arc %s -> arc %s',
-        pht('ALIAS'),
-        $command,
-        $new_command));
-
-    $new_argv = array_merge(array($new_command), $new_args);
-
-    return $this->resolveAliases($workflows, $new_argv, $config);
-  }
-
-  private function logTrace($label, $message) {
-    echo tsprintf(
-      "**<bg:magenta> %s </bg>** %s\n",
-      $label,
-      $message);
+    return $argv;
   }
 
 }