Devserver: allow SubversionFileSystem to be pinned to a specific rev on construction

chrome/common/extensions/docs/server2/PRESUBMIT.py

 # Copyright (c) 2012 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.
 
 """Presubmit script for changes affecting extensions docs server
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 19 matching lines @@
   import build_server
   build_server.main()
 finally:
   sys.path = SYS_PATH
 
 WHITELIST = [ r'.+_test.py$' ]
 # The integration tests are selectively run from the PRESUBMIT in
 # chrome/common/extensions.
 BLACKLIST = [ r'integration_test.py$' ]
 
+def _WarnIfAppYamlHasntChanged(input_api, output_api):
+  if any(path.endswith('app.yaml') for path in input_api.LocalPaths()):
+    return []
+  return [output_api.PresubmitPromptOrNotify('''
+**************************************************
+CHANGE DETECTED IN SERVER2 WITHOUT APP.YAML UPDATE
+**************************************************
+Maybe this is ok? Follow this simple guide:
+
+Q: Does this change any data that might get stored?
+  * Did you add/remove/update a field to a data source?
+  * Did you add/remove/update some data that gets sent to templates?
+  * Is this change to support a new feature in the templates?
+  * Does this change include changes to templates?
+Yes? Bump the middle version, i.e. 2-5-2 -> 2-6-2.
+   THIS WILL CAUSE THE CURRENTLY RUNNING SERVER TO STOP UPDATING.
+   PUSH THE NEW VERSION ASAP.
+No? Continue.
+
+Q: Is this a non-trivial change to the server?
+Yes? Bump the end version, i.e. 2-5-2 -> 2-5-3.
+No? Are you sure? How much do you bet? This can't be rolled back...

[方觉(Fang Jue), 2013/05/10 08:49:17]

Different versions have separate object stores, which means it can be rolled
back if no change is made to the templates. Does server only change really need
to bump the middle version?

Since 'THIS WILL CAUSE THE CURRENTLY RUNNING SERVER TO STOP UPDATING', the
middle version shouldn't be changed more often than necessary? I think only
patches with both server changes and template changes need to bump it?

[not at google - send to devlin, 2013/05/10 17:49:58]

Yep, this comment is *slightly* misleading. In a follow-up I'm going to
implement not pinning subversion unless one of the first two numbers change,
however, I just need to get this part in for now.

+
+Q: Is this a spelling correction? New test? Better comments?
+Yes? Ok fine. Ignore this warning.
+No? I guess this presubmit check doesn't work.
+''')]
+
+def _RunPresubmit(input_api, output_api):
+  return (
+      _WarnIfAppYamlHasntChanged(input_api, output_api) +
+      input_api.canned_checks.RunUnitTestsInDirectory(
+          input_api, output_api, '.', whitelist=WHITELIST, blacklist=BLACKLIST)
+  )
+
 def CheckChangeOnUpload(input_api, output_api):
-  return input_api.canned_checks.RunUnitTestsInDirectory(
-      input_api, output_api, '.', whitelist=WHITELIST, blacklist=BLACKLIST)
+  return _RunPresubmit(input_api, output_api)
 
 def CheckChangeOnCommit(input_api, output_api):
-  return input_api.canned_checks.RunUnitTestsInDirectory(
-      input_api, output_api, '.', whitelist=WHITELIST, blacklist=BLACKLIST)
+  return _RunPresubmit(input_api, output_api)