git_test_utils: Automatic commit dates are now in UTC.

This fixes the test being dependent on the system time, and undefined
behaviour resulting from negative timestamps in positive-offset
timezones.

BUG=581895

Review URL: https://codereview.chromium.org/1640973002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298438 0039d316-1c4b-4281-b951-d872f2087c98

testing_support/git_test_utils.py

@@ -93,6 +93,24 @@ class OrderedSet(collections.MutableSet):
     return key
 
 
+class UTC(datetime.tzinfo):
+  """UTC time zone.
+
+  from https://docs.python.org/2/library/datetime.html#tzinfo-objects
+  """
+  def utcoffset(self, dt):
+    return datetime.timedelta(0)
+
+  def tzname(self, dt):
+    return "UTC"
+
+  def dst(self, dt):
+    return datetime.timedelta(0)
+
+
+UTC = UTC()
+
+
 class GitRepoSchema(object):
   """A declarative git testing repo.
 
@@ -267,7 +285,7 @@ class GitRepo(object):
     """
     self.repo_path = tempfile.mkdtemp(dir=self.BASE_TEMP_DIR)
     self.commit_map = {}
-    self._date = datetime.datetime(1970, 1, 1)
+    self._date = datetime.datetime(1970, 1, 1, tzinfo=UTC)
 
     self.to_schema_refs = ['--branches']
 
@@ -360,6 +378,11 @@ class GitRepo(object):
     except subprocess.CalledProcessError as e:
       return self.COMMAND_OUTPUT(e.returncode, e.output)
 
+  def show_commit(self, commit_name, format_string):
+    """Shows a commit (by its schema name) with a given format string."""
+    return self.git('show', '-q', '--pretty=format:%s' % format_string,
+                    self[commit_name]).stdout
+
   def git_commit(self, message):
     return self.git('commit', '-am', message, env=self.get_git_commit_env())
 

tests/git_common_test.py

@@ -772,6 +772,33 @@ class GitMakeWorkdir(git_test_utils.GitRepoReadOnlyTestBase, GitCommonTestBase):
     self.assertFalse(os.path.islink(os.path.join(workdir, '.git', 'HEAD')))
 
 
+class GitTestUtilsTest(git_test_utils.GitRepoReadOnlyTestBase):
+  REPO_SCHEMA = """
+  A B
+  """
+
+  COMMIT_A = {
+    'file1': {'data': 'file1'},
+  }
+
+  COMMIT_B = {
+    'file1': {'data': 'file1 changed'},
+  }
+
+  def testAutomaticCommitDates(self):
+    # The dates should start from 1970-01-01 and automatically increment. They
+    # must be in UTC (otherwise the tests are system-dependent, and if your
+    # local timezone is positive, timestamps will be <0 which causes bizarre
+    # behaviour in Git; http://crbug.com/581895).
+    self.assertEquals('Author McAuthorly 1970-01-01 00:00:00 +0000',
+                      self.repo.show_commit('A', format_string='%an %ai'))
+    self.assertEquals('Charles Committish 1970-01-02 00:00:00 +0000',
+                      self.repo.show_commit('A', format_string='%cn %ci'))
+    self.assertEquals('Author McAuthorly 1970-01-03 00:00:00 +0000',
+                      self.repo.show_commit('B', format_string='%an %ai'))
+    self.assertEquals('Charles Committish 1970-01-04 00:00:00 +0000',
+                      self.repo.show_commit('B', format_string='%cn %ci'))
+
 
 if __name__ == '__main__':
   sys.exit(coverage_utils.covered_main(