Fix toplevel_root parsing in trychange.py

In https://codereview.chromium.org/11574007/ I attempted to make it possible to use the TRYSERVER_ROOT setting in codereview.settings. It seems like some checkouts ran into errors with it not finding the codereview.settings file when it was parsed. This is probably due to the fact that the following call chain reads the self.toplevel_root variable:
_GclStyleSettings -> GetCodeReviewSetting -> ReadRootFile
By moving _GclStyleSettings up before self.toplevel_root is set probably causes this.

This CL attempts to correct this.

BUG=none, but try job upload fails for some users.
TEST=submitting try job to locally running try server.


Review URL: https://chromiumcodereview.appspot.com/11571052

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@173928 0039d316-1c4b-4281-b951-d872f2087c98

trychange.py

@@ -149,8 +149,12 @@ class SCM(object):
     return self.codereview_settings.get(key, '')
 
   def _GclStyleSettings(self):
-    """Set default settings based on the gcl-style settings from the
+    """Set default settings based on the gcl-style settings from the repository.
-    repository."""
+
+    The settings in the self.options object will only be set if no previous
+    value exists (i.e. command line flags to the try command will override the
+    settings in codereview.settings).
+    """
     settings = {
       'port': self.GetCodeReviewSetting('TRYSERVER_HTTP_PORT'),
       'host': self.GetCodeReviewSetting('TRYSERVER_HTTP_HOST'),
@@ -162,14 +166,14 @@ class SCM(object):
     logging.info('\n'.join(['%s: %s' % (k, v)
                             for (k, v) in settings.iteritems() if v]))
     for (k, v) in settings.iteritems():
+      # Avoid overwriting options already set using command line flags.
       if v and getattr(self.options, k) is None:
         setattr(self.options, k, v)
 
   def AutomagicalSettings(self):
     """Determines settings based on supported code review and checkout tools.
     """
-    self._GclStyleSettings()
+    # Try to find gclient or repo root first.
-    # Try to find gclient or repo root.
     if not self.options.no_search:
       self.toplevel_root = gclient_utils.FindGclientRoot(self.checkout_root)
       if self.toplevel_root:
@@ -181,10 +185,17 @@ class SCM(object):
           logging.info('Found .repo dir at %s'
                        % os.path.dirname(self.toplevel_root))
 
+      # Parse TRYSERVER_* settings from codereview.settings before falling back
+      # on setting self.options.root manually further down. Otherwise
+      # TRYSERVER_ROOT would never be used in codereview.settings.
+      self._GclStyleSettings()
+
       if self.toplevel_root and not self.options.root:
         assert os.path.abspath(self.toplevel_root) == self.toplevel_root
         self.options.root = gclient_utils.PathDifference(self.toplevel_root,
                                                          self.checkout_root)
+    else:
+      self._GclStyleSettings()
 
   def ReadRootFile(self, filename):
     cur = self.checkout_root