Export task point values as double, not int

Summary:
See <https://discourse.phabricator-community.org/t/maniphest-non-integer-point-values-in-csv-export/1443>.

We currently export the Maniphest "points" field as an integer, but allow it to accept decimal values (e.g. "6.25").

Also fix a bug where we wouldn't roll over from "..., X, Y, Z, AA, AB, ..." correctly for Excel column names if sheet had more than 26 columns.

Test Plan:
  - Set a task point value to 6.25.
  - Exported to text, JSON, XLS.
  - Saw 6.25 represented accurately in exports.
  - Exported an excel sheet with 27+ columns.
  - Manually printed the first 200 column names to check that the algorithm looks correct.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D19434

src/__phutil_library_map__.php

@@ -2882,6 +2882,7 @@ phutil_register_library_map(array(
     'PhabricatorDocumentRef' => 'applications/files/document/PhabricatorDocumentRef.php',
     'PhabricatorDocumentRenderingEngine' => 'applications/files/document/render/PhabricatorDocumentRenderingEngine.php',
     'PhabricatorDoorkeeperApplication' => 'applications/doorkeeper/application/PhabricatorDoorkeeperApplication.php',
+    'PhabricatorDoubleExportField' => 'infrastructure/export/field/PhabricatorDoubleExportField.php',
     'PhabricatorDraft' => 'applications/draft/storage/PhabricatorDraft.php',
     'PhabricatorDraftDAO' => 'applications/draft/storage/PhabricatorDraftDAO.php',
     'PhabricatorDraftEngine' => 'applications/transactions/draft/PhabricatorDraftEngine.php',
@@ -8540,6 +8541,7 @@ phutil_register_library_map(array(
     'PhabricatorDocumentRef' => 'Phobject',
     'PhabricatorDocumentRenderingEngine' => 'Phobject',
     'PhabricatorDoorkeeperApplication' => 'PhabricatorApplication',
+    'PhabricatorDoubleExportField' => 'PhabricatorExportField',
     'PhabricatorDraft' => 'PhabricatorDraftDAO',
     'PhabricatorDraftDAO' => 'PhabricatorLiskDAO',
     'PhabricatorDraftEngine' => 'Phobject',

src/applications/maniphest/query/ManiphestTaskSearchEngine.php

@@ -516,7 +516,7 @@ final class ManiphestTaskSearchEngine
     );
 
     if (ManiphestTaskPoints::getIsEnabled()) {
-      $fields[] = id(new PhabricatorIntExportField())
+      $fields[] = id(new PhabricatorDoubleExportField())
         ->setKey('points')
         ->setLabel('Points');
     }

src/infrastructure/export/field/PhabricatorDoubleExportField.php

@@ -0,0 +1,25 @@
+<?php
+
+final class PhabricatorDoubleExportField
+  extends PhabricatorExportField {
+
+  public function getNaturalValue($value) {
+    if ($value === null) {
+      return $value;
+    }
+
+    return (double)$value;
+  }
+
+  /**
+   * @phutil-external-symbol class PHPExcel_Cell_DataType
+   */
+  public function formatPHPExcelCell($cell, $style) {
+    $cell->setDataType(PHPExcel_Cell_DataType::TYPE_NUMERIC);
+  }
+
+  public function getCharacterWidth() {
+    return 8;
+  }
+
+}

src/infrastructure/export/format/PhabricatorExcelExportFormat.php

@@ -155,8 +155,12 @@ EOHELP
     return $this->sheet;
   }
 
+
+  /**
+   * @phutil-external-symbol class PHPExcel_Cell
+   */
   private function getCellName($col, $row = null) {
-    $col_name = chr(ord('A') + $col);
+    $col_name = PHPExcel_Cell::stringFromColumnIndex($col);
 
     if ($row === null) {
       return $col_name;