git cl: allow to forcibly bypass cache and fetch CL description.

R=kbr@chromium.org
BUG=633572,688765

Change-Id: I2ce6530148bc2f00fe9f6a80aaccc520c69a2f83
Reviewed-on: https://chromium-review.googlesource.com/439186
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>

git_cl.py

@@ -1355,8 +1355,8 @@ class Changelist(object):
       return None
     return '%s/%s' % (self._codereview_impl.GetCodereviewServer(), issue)
 
-  def GetDescription(self, pretty=False):
-    if not self.has_description:
+  def GetDescription(self, pretty=False, force=False):
+    if not self.has_description or force:
       if self.GetIssue():
         self.description = self._codereview_impl.FetchDescription()
       self.has_description = True

tests/git_cl_test.py

@@ -173,6 +173,16 @@ class SystemExitMock(Exception):
 
 
 class TestGitClBasic(unittest.TestCase):
+  def test_get_description(self):
+    cl = git_cl.Changelist(issue=1, codereview='rietveld',
+                           codereview_host='host')
+    cl.description = 'x'
+    cl.has_description = True
+    cl._codereview_impl.FetchDescription = lambda: 'y'
+    self.assertEquals(cl.GetDescription(), 'x')
+    self.assertEquals(cl.GetDescription(force=True), 'y')
+    self.assertEquals(cl.GetDescription(), 'y')
+
   def _test_ParseIssueUrl(self, func, url, issue, patchset, hostname, fail):
     parsed = urlparse.urlparse(url)
     result = func(parsed)