Add 76 column reference in git cl upload message

Adds an extra line to the default text description to help judge whether the
76 character recommended limit is being passed.

Review URL: https://chromiumcodereview.appspot.com/15670012

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@203314 0039d316-1c4b-4281-b951-d872f2087c98

git_cl.py

@@ -864,6 +864,8 @@ class ChangeDescription(object):
       '# Enter a description of the change.\n'
       '# This will be displayed on the codereview site.\n'
       '# The first line will also be used as the subject of the review.\n'
+      '#----------------------This line is 76 characters long'
+      '----------------------\n'
     ) + self._description
 
     if '\nBUG=' not in self._description:

tests/git_cl_test.py

@@ -385,7 +385,9 @@ class TestGitCl(TestCase):
       self.assertEquals(
           '# Enter a description of the change.\n'
           '# This will be displayed on the codereview site.\n'
-          '# The first line will also be used as the subject of the review.\n' +
+          '# The first line will also be used as the subject of the review.\n'
+          '#----------------------This line is 76 characters long'
+          '----------------------\n' +
           expected_description,
           desc)
       return returned_description