Presubmit: add PRESUBMIT=false to non-master branch changes

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.
 """
@@ skipping 325 matching lines @@
 def PostUploadHook(cl, change, output_api):
   """git cl upload will call this hook after the issue is created/modified.
 
   This hook does the following:
   * Adds a link to preview docs changes if there are any docs changes in the CL.
   * Adds 'NOTRY=true' if the CL contains only docs changes.
   * Adds 'NOTREECHECKS=true' for non master branch changes since they do not
     need to be gated on the master branch's tree.
   * Adds 'NOTRY=true' for non master branch changes since trybots do not yet
     work on them.
+  * Adds 'NOPRESUBMIT=true' for non master branch changes since those don't
+    run the presubmit checks.
   """
 
   results = []
   atleast_one_docs_change = False
   all_docs_changes = True
   for affected_file in change.AffectedFiles():
     affected_file_path = affected_file.LocalPath()
     file_path, _ = os.path.splitext(affected_file_path)
     if 'site' == file_path.split(os.path.sep)[0]:
       atleast_one_docs_change = True
@@ skipping 42 matching lines @@
                 'Branch changes do not need to rely on the master branch\'s '
                 'tree status. Automatically added \'NOTREECHECKS=true\' to the '
                 'CL\'s description'))
       if not re.search(
           r'^NOTRY=true$', new_description, re.M | re.I):
         new_description += "\nNOTRY=true"
         results.append(
             output_api.PresubmitNotifyResult(
                 'Trybots do not yet work for non-master branches. '
                 'Automatically added \'NOTRY=true\' to the CL\'s description'))
+      if not re.search(
+          r'^NOPRESUBMIT=true$', new_description, re.M | re.I):
+        new_description += "\nNOPRESUBMIT=true"
+        results.append(
+            output_api.PresubmitNotifyResult(
+                'Branch changes do not run the presubmit checks.'))
 
     # Read and process the HASHTAGS file.
     hashtags_fullpath = os.path.join(change._local_root, 'HASHTAGS')
     with open(hashtags_fullpath, '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]
@@ skipping 59 matching lines @@
     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