bot_update: Set user.{name,email} when applying patch refs.

git rebase complains when user name/email has not been configured, as was
the case for the Chromium trybot.

Bug: 643346
Change-Id: Iab7dac0a98608e09b63a53d5bacb98925701fbfd
Reviewed-on: https://chromium-review.googlesource.com/1031524
Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -339,6 +339,11 @@ def gclient_sync(
   fd, gclient_output_file = tempfile.mkstemp(suffix='.json')
   os.close(fd)
 
+  # Some bots don't have git user name/email configured, which causes problems
+  # when rebasing.
+  git('config', 'user.name', 'chrome-bot')
+  git('config', 'user.email', 'chrome-bot@chromium.org')
+
   args = ['sync', '--verbose', '--reset', '--force',
          '--ignore_locks', '--output-json', gclient_output_file,
          '--nohooks', '--noprehooks', '--delete_unversioned_trees']

recipes/trigger_recipe_roller.txt

@@ -1,4 +1,4 @@
-No-op file. Edit this to kick recipes. (Did they do something wrong?)
+No-op file. Edit this to kick recipes.
 
 This is a beginning of a story in this silly file.
 Once upon a time, a budding web browser dev team needed a CI system.