Add post upload hook to substitute hashtags for their mapped text

PRESUBMIT.py

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 
 """Top-level presubmit script for Skia.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
+import csv
 import fnmatch
 import os
 import re
 import subprocess
 import sys
 import traceback
 
 
 REVERT_CL_SUBJECT_PREFIX = 'Revert '
 
@@ skipping 333 matching lines @@
                 'tree status. Automatically added \'NOTREECHECKS=true\' to the '
                 'CL\'s description'))
       if not re.search(
           r'^NOTRY=true$', new_description, re.M | re.I):
         new_description += "\nNOTRY=true"
         results.append(
             output_api.PresubmitNotifyResult(
                 'Trybots do not yet work for non-master branches. '
                 'Automatically added \'NOTRY=true\' to the CL\'s description'))
 
+    # Read and process the HASHTAGS file.
+    with open('HASHTAGS', 'rb') as hashtags_csv:
+      hashtags_reader = csv.reader(hashtags_csv, delimiter=',')
+      for row in hashtags_reader:
+        if not row or row[0].startswith('#'):
+          # Ignore empty lines and comments
+          continue
+        hashtag = row[0]
+        mapped_text = row[1]
+        # Search for the hashtag in the description.
+        if re.search('#%s' % hashtag, new_description, re.M | re.I):
+          # Add the mapped text if it does not already exist in the description.
+          if not re.search(r'^%s$' % mapped_text, new_description, re.M | re.I):
+            new_description += '\n%s' % mapped_text
+            results.append(
+                output_api.PresubmitNotifyResult(
+                    'Found \'#%s\', automatically added \'%s\' to the CL\'s '
+                    'description' % (hashtag, mapped_text)))
 
     # If the description has changed update it.
     if new_description != original_description:
       rietveld_obj.update_description(issue, new_description)
 
     return results
 
 
 def CheckChangeOnCommit(input_api, output_api):
   """Presubmit checks for the change on commit.
 
   The following are the presubmit checks:
   * Check change has one and only one EOL.
   * Ensures that the Skia tree is open in
     http://skia-tree-status.appspot.com/. Shows a warning if it is in 'Caution'
     state and an error if it is in 'Closed' state.
   """
   results = []
   results.extend(_CommonChecks(input_api, output_api))
   results.extend(
       _CheckTreeStatus(input_api, output_api, json_url=(
           SKIA_TREE_STATUS_URL + '/banner-status?format=json')))
   results.extend(_CheckLGTMsForPublicAPI(input_api, output_api))
   results.extend(_CheckOwnerIsInAuthorsFile(input_api, output_api))
   return results