Make "--auto" the default for "arc diff"

Summary:
NOTE: This is a disruptive change to how 'arc diff' behaves by default.

Many years ago, Differential (then DiffCamp) supported SVN. Someone added a "-i" mode to the "diffcamp" script so you could "git show | diffcamp -i", and thus we were
forever bound to storing metadata in commit messages.

But this isn't a common use case outside of Facebook + git-svn, and isn't very flexible. We now have a great deal of flexibility to identify revisions based on
hashes, branch names, etc, and to sync metdata from web to CLI and back. I want to jettison the commit-message-bound artifacts of the tool's history, and move to a
more flexible, modern workflow.

I added "--auto" a while ago, which figures out if you want to create or update a diff automatically, and then prompts you for whatever data it needs, reading
information if it can from commit messages in the range. This is a vastly better workflow in general, especially for SVN and Mercurial users (who currently need to
jump to the web UI to create revisions). It's better for git users too, since they don't need to use template commits and don't have to muck with or configure
templates. However, it's a nontrivial change to git users' core workflow that is clearly different in more ways than it is clearly better.

  - This might be contentious, but probably not toooo much, I hope?
  - I also deleted the (fairly ridiculous) workflow where we sync commit message changes from the working copy. I think two or three people will be REALLY upset about
this but I have no sympathy. "--edit" covers this and has been around for like two years now, and making the commit message and web dual-authoritative was always a bad
idea that we only ever half-accommodated anyway (see giant swaths of removed TOOD nonsense).

Test Plan:
  - I've been using "--auto" exclusively for like a month, it seems to work well.
  - Created/updated SVN, Git and HG diffs with "arc diff" under this workflow.

Reviewers: btrahan, jungejason, nh

Reviewed By: btrahan

CC: Makinde, vrana, zeeg, mbautin, aran, yairlivne, 20after4

Maniphest Tasks: T614

Differential Revision: https://secure.phabricator.com/D2080

src/workflow/diff/ArcanistDiffWorkflow.php

@@ -175,13 +175,6 @@ EOTEXT
         'param' => 'revision_id',
         'help'  => "Always update a specific revision.",
       ),
-      'auto' => array(
-        'help' => "(Unstable!) Heuristically select --create or --update. ".
-                  "This may become the default behvaior of arc.",
-        'conflicts' => array(
-          'raw',
-        ),
-      ),
       'nounit' => array(
         'help' =>
           "Do not run unit tests.",
@@ -380,61 +373,22 @@ EOTEXT
             'edit' => true,
             'fields' => array(),
           ));
-        $remote_message = ArcanistDifferentialCommitMessage::newFromRawCorpus(
-          $remote_corpus);
-        $remote_message->pullDataFromConduit($conduit);
-
-        $sync = array('title', 'summary', 'testPlan');
-        foreach ($sync as $field) {
-          $local = $message->getFieldValue($field);
-          $remote_message->setFieldValue($field, $local);
-        }
 
         $should_edit = $this->getArgument('edit');
-
-/*
-
-  TODO: This is a complicated mess. We need to move to storing a checksum
-  of the non-auto-sync fields as they existed at original diff time and using
-  changes from that to detect user edits, not comparison of the client and
-  server values since they diverge without user edits (because of Herald
-  and explicit server-side user changes).
-
-        if (!$should_edit) {
-          $local_sum = $message->getChecksum();
-          $remote_sum = $remote_message->getChecksum();
-          if ($local_sum != $remote_sum) {
-            $prompt =
-              "You have made local changes to your commit message. Arcanist ".
-              "ignores most local changes. Instead, use the '--edit' flag to ".
-              "edit revision information. Edit revision information now?";
-            $should_edit = phutil_console_confirm(
-              $prompt,
-              $default_no = false);
-          }
-        }
-*/
-
-        $revision['fields'] = $remote_message->getFields();
-
         if ($should_edit) {
-          $updated_corpus = $conduit->callMethodSynchronous(
+          $new_text = id(new PhutilInteractiveEditor($remote_corpus))
-            'differential.getcommitmessage',
-            array(
-              'revision_id' => $message->getRevisionID(),
-              'edit' => true,
-              'fields' => $message->getFields(),
-            ));
-          $new_text = id(new PhutilInteractiveEditor($updated_corpus))
             ->setName('differential-edit-revision-info')
             ->editInteractively();
           $new_message = ArcanistDifferentialCommitMessage::newFromRawCorpus(
             $new_text);
-          $new_message->pullDataFromConduit($conduit);
+        } else {
-
+          $new_message = ArcanistDifferentialCommitMessage::newFromRawCorpus(
-          $revision['fields'] = $new_message->getFields();
+            $remote_corpus);
         }
 
+        $new_message->pullDataFromConduit($conduit);
+        $revision['fields'] = $new_message->getFields();
+
         $revision['id'] = $message->getRevisionID();
         $this->revisionID = $revision['id'];
 
@@ -559,10 +513,6 @@ EOTEXT
       return false;
     }
 
-    if ($this->getArgument('auto')) {
-      return false;
-    }
-
     if ($this->getArgument('use-commit-message')) {
       return false;
     }
@@ -1233,7 +1183,6 @@ EOTEXT
   private function buildCommitMessage() {
     $is_create = $this->getArgument('create');
     $is_update = $this->getArgument('update');
-    $is_auto   = $this->getArgument('auto');
     $is_raw = $this->isRawDiffSource();
     $is_message = $this->getArgument('use-commit-message');
 
@@ -1241,7 +1190,7 @@ EOTEXT
       return $this->getCommitMessageFromCommit($is_message);
     }
 
-    if ($is_auto) {
+    if (!$is_raw && !$is_create && !$is_update) {
       $repository_api = $this->getRepositoryAPI();
       $revisions = $repository_api->loadWorkingCopyDifferentialRevisions(
         $this->getConduit(),
@@ -1271,21 +1220,13 @@ EOTEXT
       } else {
         return $this->getCommitMessageFromUser();
       }
-    }
+    } else if ($is_update) {
-
-    if ($is_update) {
       return $this->getCommitMessageFromRevision($is_update);
-    }
+    } else {
-
+      // This is --raw without enough info to create a revision, so force just
-    if ($is_raw) {
+      // a diff.
       return null;
     }
-
-    if (!$this->shouldOnlyCreateDiff()) {
-      return $this->getGitCommitMessage();
-    }
-
-    return null;
   }
 
 
@@ -1359,10 +1300,13 @@ EOTEXT
     }
 
     $issues = array(
-      'Describe this revision.',
+      'NEW DIFFERENTIAL REVISION',
+      'Describe the changes in this new revision.',
       '',
-      'If you intended to update a existing revision, use ',
+      'arc could not identify any existing revision in your working copy.',
-      '`arc diff --update <revision>`.',
+      'If you intended to update an existing revision, use:',
+      '',
+      '  $ arc diff --update <revision>',
     );
     if ($notes) {
       $issues = array_merge($issues, array(''), $notes);
@@ -1551,100 +1495,6 @@ EOTEXT
     return $comments;
   }
 
-
-  /**
-   * @task message
-   */
-  private function getGitCommitMessage() {
-    $conduit = $this->getConduit();
-    $repository_api = $this->getRepositoryAPI();
-
-    $commit_messages = $this->getLocalGitCommitMessages();
-
-    $problems = array();
-    $parsed = array();
-    $hashes = array();
-    foreach ($commit_messages as $key => $change) {
-      $problems[$key] = array();
-      $hashes[$key] = $change->getCommitHash();
-
-      try {
-        $message = ArcanistDifferentialCommitMessage::newFromRawCorpus(
-          $change->getMetadata('message'));
-
-        $message->pullDataFromConduit($conduit);
-
-        $parsed[$key] = $message;
-      } catch (ArcanistDifferentialCommitMessageParserException $ex) {
-        foreach ($ex->getParserErrors() as $problem) {
-          $problems[$key][] = $problem;
-        }
-        continue;
-      }
-    }
-
-    $valid = array();
-    foreach ($problems as $key => $problem_list) {
-      if ($problem_list) {
-        continue;
-      }
-      $valid[$key] = $parsed[$key];
-    }
-
-    $blessed = null;
-    if (count($valid) == 1) {
-      $blessed = head($valid);
-    } else if (count($valid) > 1) {
-      echo phutil_console_wrap(
-        "Changes in the specified commit range include more than one commit ".
-        "with a valid template commit message. Choose the message you want ".
-        "to use (you can also use the -C flag).\n\n");
-      foreach ($valid as $key => $message) {
-        $hash = substr($hashes[$key], 0, 7);
-        $title = $commit_messages[$key]->getMetadata('message');
-        $title = head(explode("\n", trim($title)));
-        $title = phutil_utf8_shorten($title, 64);
-        echo "    {$hash}  {$title}\n";
-      }
-
-      do {
-        $choose = phutil_console_prompt('Use which commit message?');
-        foreach ($valid as $key => $message) {
-          if (!strncmp($hashes[$key], $choose, strlen($choose))) {
-            $blessed = $valid[$key];
-            break;
-          }
-        }
-      } while (!$blessed);
-    }
-
-    if (!$blessed) {
-      $desc = implode("\n", array_mergev($problems));
-      if (count($problems) > 1) {
-        throw new ArcanistUsageException(
-          "All changes between the specified commits have template parsing ".
-          "problems:\n\n".$desc."\n\nIf you only want to create a diff ".
-          "(not a revision), use --preview to ignore commit messages.");
-      } else if (count($problems) == 1) {
-        $user_guide = 'http://phabricator.com/docs/phabricator/'.
-                      'article/Arcanist_User_Guide.html';
-        throw new ArcanistUsageException(
-          "Commit message is not properly formatted:\n\n".$desc."\n\n".
-          "You should use the standard git commit template to provide a ".
-          "commit message. If you only want to create a diff (not a ".
-          "revision), use --preview to ignore commit messages.\n\n".
-          "See this document for instructions on configuring the commit ".
-          "template:\n\n    {$user_guide}\n");
-      }
-    }
-
-    if ($blessed) {
-      $this->validateCommitMessage($blessed);
-    }
-
-    return $blessed;
-  }
-
   private function getLocalGitCommitMessages() {
     $repository_api = $this->getRepositoryAPI();
     $parser = new ArcanistDiffParser();
@@ -1677,6 +1527,8 @@ EOTEXT
       return $this->getGitCreateFields();
     }
 
+    // TODO: Load default fields in Mercurial.
+
     return $empty;
   }