[Wilds] Sort of make "arc help" work again

Summary:
Ref T13098. This makes "arc help" kind-of sort-of work again.

Previously, "arc help" was completely custom and hard-coded. Now it just proxies the generic libphutil "help" workflow. The two flows are substantially similar, although old `arc help` was a little more brief than the new version is. The old `arc help --full` was more similar to the default:

| Command | Old Behavior | New Behavior |
|---|---|---|
| `arc` | Tells you to run `arc help`. | Plan: make this a bit richer and give a quick summary of workflows. |
| `arc help` | Gives you a summary of workflows. | Gives you a detailed list of workflows. |
| `arc help --full` | Gives you a detailed list of workflows. | No such flag. |
| `arc --help` | Same as `arc help`. | Same as `arc`. Plan: same as `arc help`. |
| `arc help <workflow>` | Full workflow help. | Full workflow help. |
| `arc <workflow> --help` | As above. | As above. |

Overall this is largely the same and lets us delete a bunch of code.

Test Plan:
Ran `arc`, `arc help`, `arc --help`, `arc --help diff`, `arc diff --help`, `arc help diff`, `arc help help`.

These commands largely do something sensible now, with caveats per above.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13098

Differential Revision: https://secure.phabricator.com/D19679

scripts/init/init-arcanist.php

@@ -75,6 +75,17 @@ final class ArcanistRuntime {
 
     $unconsumed_argv = $args->getUnconsumedArgumentVector();
 
+    if (!$unconsumed_argv) {
+      // TOOLSETS: This means the user just ran "arc" or some other top-level
+      // toolset without any workflow argument. We should give them a summary
+      // of the toolset, a list of workflows, and a pointer to "arc help" for
+      // more details.
+
+      // A possible exception is "arc --help", which should perhaps pass
+      // through and act like "arc help".
+      throw new PhutilArgumentUsageException(pht('Choose a workflow!'));
+    }
+
     $result = $this->resolveAliases($workflows, $unconsumed_argv, $config);
     if (is_int($result)) {
       return $result;

src/__phutil_library_map__.php

@@ -187,6 +187,7 @@ phutil_register_library_map(array(
     'ArcanistHLintLinter' => 'lint/linter/ArcanistHLintLinter.php',
     'ArcanistHLintLinterTestCase' => 'lint/linter/__tests__/ArcanistHLintLinterTestCase.php',
     'ArcanistHardpointLoader' => 'loader/ArcanistHardpointLoader.php',
+    'ArcanistHelpWorkflow' => 'toolset/ArcanistHelpWorkflow.php',
     'ArcanistHexadecimalNumericScalarCasingXHPASTLinterRule' => 'lint/linter/xhpast/rules/ArcanistHexadecimalNumericScalarCasingXHPASTLinterRule.php',
     'ArcanistHexadecimalNumericScalarCasingXHPASTLinterRuleTestCase' => 'lint/linter/xhpast/rules/__tests__/ArcanistHexadecimalNumericScalarCasingXHPASTLinterRuleTestCase.php',
     'ArcanistHgClientChannel' => 'hgdaemon/ArcanistHgClientChannel.php',
@@ -639,6 +640,7 @@ phutil_register_library_map(array(
     'ArcanistHLintLinter' => 'ArcanistExternalLinter',
     'ArcanistHLintLinterTestCase' => 'ArcanistExternalLinterTestCase',
     'ArcanistHardpointLoader' => 'Phobject',
+    'ArcanistHelpWorkflow' => 'ArcanistWorkflow',
     'ArcanistHexadecimalNumericScalarCasingXHPASTLinterRule' => 'ArcanistXHPASTLinterRule',
     'ArcanistHexadecimalNumericScalarCasingXHPASTLinterRuleTestCase' => 'ArcanistXHPASTLinterRuleTestCase',
     'ArcanistHgClientChannel' => 'PhutilProtocolChannel',

src/toolset/ArcanistAliasWorkflow.php

@@ -132,7 +132,7 @@ EOTEXT
 
   public static function resolveAliases(
     $command,
-    ArcanistConfiguration $config,
+    ArcanistRuntime $config,
     array $argv,
     ArcanistConfigurationManager $configuration_manager) {
 

src/toolset/ArcanistHelpWorkflow.php

@@ -0,0 +1,13 @@
+<?php
+
+final class ArcanistHelpWorkflow extends ArcanistWorkflow {
+
+  public function getWorkflowName() {
+    return 'help';
+  }
+
+  public function newPhutilWorkflow() {
+    return new PhutilHelpArgumentWorkflow();
+  }
+
+}