Shorten attribute name.

Addresses:
#809 (comment).

gcloud/pubsub/test_topic.py

@@ -38,7 +38,7 @@ def test_ctor_wo_inferred_project_or_connection(self):
         self.assertEqual(topic.full_name,
                          'projects/%s/topics/%s' % (PROJECT, TOPIC_NAME))
         self.assertTrue(topic.connection is conn)
-        self.assertFalse(topic.add_timestamp_to_messages)
+        self.assertFalse(topic.timestamp_messages)
 
     def test_ctor_w_explicit_project_connection_and_timestamp(self):
         TOPIC_NAME = 'topic_name'
@@ -47,13 +47,13 @@ def test_ctor_w_explicit_project_connection_and_timestamp(self):
         topic = self._makeOne(TOPIC_NAME,
                               project=PROJECT,
                               connection=conn,
-                              add_timestamp_to_messages=True)
+                              timestamp_messages=True)
         self.assertEqual(topic.name, TOPIC_NAME)
         self.assertEqual(topic.project, PROJECT)
         self.assertEqual(topic.full_name,
                          'projects/%s/topics/%s' % (PROJECT, TOPIC_NAME))
         self.assertTrue(topic.connection is conn)
-        self.assertTrue(topic.add_timestamp_to_messages)
+        self.assertTrue(topic.timestamp_messages)
 
     def test_from_api_repr_wo_connection(self):
         from gcloud.pubsub._testing import _monkey_defaults
@@ -171,7 +171,7 @@ def _utcnow():
         PATH = 'projects/%s/topics/%s' % (PROJECT, TOPIC_NAME)
         conn = _Connection({'messageIds': [MSGID]})
         topic = self._makeOne(TOPIC_NAME, project=PROJECT, connection=conn,
-                              add_timestamp_to_messages=True)
+                              timestamp_messages=True)
         with _Monkey(MUT, _NOW=_utcnow):
             msgid = topic.publish(PAYLOAD)
         self.assertEqual(msgid, MSGID)

gcloud/pubsub/topic.py

@@ -43,21 +43,21 @@ class Topic(object):
     :param connection: the connection to use.  If not passed,
                         falls back to the default inferred from the
 
-    :type add_timestamp_to_messages: boolean
-    :param add_timestamp_to_messages: If true, the topic will add a key,
-                        ``timestamp``, to the attributes of each published
-                        method:  the value will be an RFC 3339 timestamp.
+    :type timestamp_messages: boolean
+    :param timestamp_messages: If true, the topic will add a ``timestamp`` key
+                               to the attributes of each published message:
+                               the value will be an RFC 3339 timestamp.
     """
     def __init__(self, name, project=None, connection=None,
-                 add_timestamp_to_messages=False):
+                 timestamp_messages=False):
         if project is None:
             project = get_default_project()
         if connection is None:
             connection = get_default_connection()
         self.name = name
         self.project = project
         self.connection = connection
-        self.add_timestamp_to_messages = add_timestamp_to_messages
+        self.timestamp_messages = timestamp_messages
 
     @classmethod
     def from_api_repr(cls, resource, connection=None):
@@ -122,7 +122,7 @@ def publish(self, message, **attrs):
         :rtype: str
         :returns: message ID assigned by the server to the published message
         """
-        if self.add_timestamp_to_messages:
+        if self.timestamp_messages:
             attrs['timestamp'] = '%sZ' % _NOW().isoformat()
         message_b = base64.b64encode(message).decode('ascii')
         message_data = {'data': message_b, 'attributes': attrs}