include task ids in the commit messages returned by "arc amend"

Summary:
when "arc diff" generates a revision, it attaches a task id
if one is included.  However, "arc amend" did not return a task id,
effectively stripping it from the commit message.  This diff fixes
that.

NOTE: This is dependent on revision 549 https://secure.phabricator.com/D549

Test Plan:
0. created a custom class to append Facebook task IDs to commit messages and
attached it to the differential.append-commit-message-class config variable
1. created a new diff in the www repot
2. included Task ID: 609350 in the git commit message
3. "arc diff" to generate the revision
4. "arc amend"
5. ensure that the "Task ID:" field remained in the git commit message

Reviewed By: epriestley
Reviewers: dpepper, jungejason, epriestley
CC: aran, epriestley, mgummelt
Differential Revision: 546

conf/default.conf.php

@@ -355,6 +355,12 @@ return array(
     '/.*/'      => 80,
   ),
 
+  // Class for appending custom fields to be included in the commit
+  // messages generated by "arc amend".  Should inherit
+  // DifferentialCommitMessageModifier
+  'differential.modify-commit-message-class' => null,
+
+
 // -- Maniphest ------------------------------------------------------------- //
 
   'maniphest.enabled' => true,

src/__phutil_library_map__.php

@@ -140,6 +140,7 @@ phutil_register_library_map(array(
     'DifferentialCommitMessage' => 'applications/differential/parser/commitmessage',
     'DifferentialCommitMessageData' => 'applications/differential/data/commitmessage',
     'DifferentialCommitMessageField' => 'applications/differential/data/commitmessage',
+    'DifferentialCommitMessageModifier' => 'applications/differential/data/commitmessage',
     'DifferentialCommitMessageParserException' => 'applications/differential/parser/commitmessage/exception',
     'DifferentialController' => 'applications/differential/controller/base',
     'DifferentialDAO' => 'applications/differential/storage/base',

src/applications/differential/data/commitmessage/DifferentialCommitMessageData.php

@@ -154,6 +154,15 @@ class DifferentialCommitMessageData {
     $fields[] = new DifferentialCommitMessageField('Differential Revision',
                                                    $revision->getID());
 
+    // append custom commit message fields
+    $modify_class = PhabricatorEnv::getEnvConfig(
+      'differential.modify-commit-message-class');
+
+    if ($modify_class) {
+      $modifier = newv($modify_class, array($revision));
+      $fields = $modifier->modifyFields($fields);
+    }
+
     $this->fields = $fields;
   }
 

src/applications/differential/data/commitmessage/DifferentialCommitMessageModifier.php

@@ -0,0 +1,39 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+abstract class DifferentialCommitMessageModifier {
+  protected $revision;
+
+  /**
+  * @param  DifferentialRevision The revision to generate fields for
+  */
+  public function __construct(DifferentialRevision $revision) {
+    $this->revision = $revision;
+  }
+
+  /**
+   * Implementation of this function should remove, modify, or append
+   * fields to the $fields representing the fields for the given
+   * $revision.  It should return the modified dict.  These fields are
+   * included in the commit message generated by 'arc amend'.
+   *
+   * @param  array                The array of fields to modify
+   * @return array                The updated array of fields
+   */
+  abstract public function modifyFields(array $fields);
+}

src/applications/differential/data/commitmessage/__init__.php

@@ -9,9 +9,12 @@
 phutil_require_module('phabricator', 'applications/differential/constants/action');
 phutil_require_module('phabricator', 'applications/differential/storage/comment');
 phutil_require_module('phabricator', 'applications/phid/handle/data');
+phutil_require_module('phabricator', 'infrastructure/env');
 
+phutil_require_module('phutil', 'symbols');
 phutil_require_module('phutil', 'utils');
 
 
 phutil_require_source('DifferentialCommitMessageData.php');
 phutil_require_source('DifferentialCommitMessageField.php');
+phutil_require_source('DifferentialCommitMessageModifier.php');