Use get_or_create_merge_base in git-cl-upload to correctly deal with rebased

upstreams.

In the event that users are NOT using the enhanced tooling, this is equivalent
to `git merge-base "@{u}" HEAD`. In the event that they are, this will catch
the case where their parent branch got rebased, but this branch hasn't been
rebased on the parent yet.

R=agable@chromium.org, szager@chromium.org
BUG=

Review URL: https://codereview.chromium.org/224703002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@261601 0039d316-1c4b-4281-b951-d872f2087c98

git_cl.py

@@ -35,13 +35,14 @@ import breakpad  # pylint: disable=W0611
 import clang_format
 import fix_encoding
 import gclient_utils
+import git_common
+import owners_finder
 import presubmit_support
 import rietveld
 import scm
 import subcommand
 import subprocess2
 import watchlists
-import owners_finder
 
 __version__ = '1.0'
 
@@ -551,7 +552,8 @@ or verify this branch is set up to track another (via the --track argument to
     return remote, upstream_branch
 
   def GetCommonAncestorWithUpstream(self):
-    return RunGit(['merge-base', self.GetUpstreamBranch(), 'HEAD']).strip()
+    return git_common.get_or_create_merge_base(self.GetBranch(),
+                                               self.GetUpstreamBranch())
 
   def GetUpstreamBranch(self):
     if self.upstream_branch is None:
@@ -2155,7 +2157,7 @@ def CMDtry(parser, args):
             "-bwin_rel:base_unittests:ValuesTest.*Value"))
   group.add_option(
       "-m", "--master", default='',
-      help=("Specify a try master where to run the tries."))           
+      help=("Specify a try master where to run the tries."))
   group.add_option(
       "-r", "--revision",
       help="Revision to use for the try job; default: the "

tests/git_cl_test.py

@@ -16,6 +16,7 @@ sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from testing_support.auto_stub import TestCase
 
 import git_cl
+import git_common
 import subprocess2
 
 
@@ -76,6 +77,9 @@ class TestGitCl(TestCase):
     self.mock(subprocess2, 'check_output', self._mocked_call)
     self.mock(subprocess2, 'communicate', self._mocked_call)
     self.mock(subprocess2, 'Popen', self._mocked_call)
+    self.mock(git_common, 'get_or_create_merge_base',
+              lambda *a: (
+                  self._mocked_call(['get_or_create_merge_base']+list(a))))
     self.mock(git_cl, 'FindCodereviewSettingsFile', lambda: '')
     self.mock(git_cl, 'ask_for_data', self._mocked_call)
     self.mock(git_cl.breakpad, 'post', self._mocked_call)
@@ -93,7 +97,7 @@ class TestGitCl(TestCase):
       self.assertEquals([], self.calls)
     super(TestGitCl, self).tearDown()
 
-  def _mocked_call(self, *args, **kwargs):
+  def _mocked_call(self, *args, **_kwargs):
     self.assertTrue(
         self.calls,
         '@%d  Expected: <Missing>   Actual: %r' % (self._calls_done, args))
@@ -158,7 +162,7 @@ class TestGitCl(TestCase):
       ((['git', 'symbolic-ref', 'HEAD'],), 'master'),
       ((['git', 'config', 'branch.master.merge'],), 'master'),
       ((['git', 'config', 'branch.master.remote'],), 'origin'),
-      ((['git', 'merge-base', 'master', 'HEAD'],),
+      ((['get_or_create_merge_base', 'master', 'master'],),
        'fake_ancestor_sha'),
       ] + cls._git_sanity_checks('fake_ancestor_sha', 'master') + [
       ((['git', 'rev-parse', '--show-cdup'],), ''),
@@ -538,8 +542,8 @@ class TestGitCl(TestCase):
         ((['git', 'symbolic-ref', 'HEAD'],), 'master'),
         ((['git', 'config', 'branch.master.merge'],), 'master'),
         ((['git', 'config', 'branch.master.remote'],), 'origin'),
-        ((['git',
-           'merge-base', 'master', 'HEAD'],), 'fake_ancestor_sha'),
+        ((['get_or_create_merge_base', 'master', 'master'],),
+         'fake_ancestor_sha'),
         ] + cls._git_sanity_checks('fake_ancestor_sha', 'master') + [
         ((['git', 'rev-parse', '--show-cdup'],), ''),
         ((['git', 'rev-parse', 'HEAD'],), '12345'),