Add "--period year" support.

When analysing logs spanning over years, with monthly graph points.

apachedex/__init__.py

@@ -367,6 +367,11 @@ class AggregateSiteUrl(argparse.Action):
         action = partial(action, prefix=value.count('/') + offset)
       dest.append((value, action))
 
+def _asMonthString(timestamp):
+  dt, tz = timestamp.split(' ')
+  _, month, year = dt.split(':', 1)[0].split('/')
+  return '%s/%02i' % (year, MONTH_VALUE_DICT[month])
+
 def _asDayString(timestamp):
   dt, tz = timestamp.split(' ')
   day, month, year = dt.split(':', 1)[0].split('/')
@@ -379,6 +384,7 @@ def _asHourString(timestamp):
   return '%s/%02i/%s %s' % (year, MONTH_VALUE_DICT[month], day, hour)
 
 period_parser = {
+  'year': (_asMonthString, lambda x: x.split('/', 1)[0], 'month'),
   'month': (_asDayString, lambda x: '/'.join(x.split('/', 2)[:2]), 'day'),
   'day': (_asHourString, lambda x: x.split(' ')[0], 'hour'),
 }