Mock out date call in push-to-trunk script for testability.

tools/push-to-trunk/common_includes.py

Index: tools/push-to-trunk/common_includes.py
diff --git a/tools/push-to-trunk/common_includes.py b/tools/push-to-trunk/common_includes.py
index a2f0748f509be54ae8c3091b8529793a3787410f..ba23314e070bad39fe71a9b7fc4afb2de1c5b987 100644
--- a/tools/push-to-trunk/common_includes.py
+++ b/tools/push-to-trunk/common_includes.py
@@ -26,6 +26,7 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+import datetime
 import os
 import re
 import subprocess
@@ -202,9 +203,12 @@ class SideEffectHandler(object):
     finally:
       url_fh.close()
 
-  def Sleep(seconds):
+  def Sleep(self, seconds):
     time.sleep(seconds)
 
+  def GetDate(self):
+    return datetime.date.today().strftime("%Y-%m-%d")
+
 DEFAULT_SIDE_EFFECT_HANDLER = SideEffectHandler()
 
 
@@ -286,6 +290,9 @@ class Step(object):
     cmd = lambda: self._side_effect_handler.ReadURL(url)
     return self.Retry(cmd, retry_on, wait_plan)
 
+  def GetDate(self):
+    return self._side_effect_handler.GetDate()
+
   def Die(self, msg=""):
     if msg != "":
       print "Error: %s" % msg