Add a fallback to origin/trunk too when the branch is not tracked.

scm.py

 # Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """SCM-specific utility classes."""
 
 import glob
 import os
 import re
 import shutil
@@ skipping 200 matching lines @@
         ['config', 'branch.%s.merge' % branch], in_directory=cwd,
         error_ok=True)[0].strip()
     if upstream_branch:
       remote = GIT.Capture(
           ['config', 'branch.%s.remote' % branch],
           in_directory=cwd, error_ok=True)[0].strip()
     else:
       # Fall back on trying a git-svn upstream branch.
       if GIT.IsGitSvn(cwd):
         upstream_branch = GIT.GetSVNBranch(cwd)
-      # Fall back on origin/master if it exits.
-      elif GIT.Capture(['branch', '-r'], in_directory=cwd
-                      )[0].split().count('origin/master'):
-        remote = 'origin'
-        upstream_branch = 'refs/heads/master'
       else:
-        remote = None
-        upstream_branch = None
+        # Else, try to guess the origin remote.
+        remote_branches = GIT.Capture(
+            ['branch', '-r'], in_directory=cwd)[0].split()
+        if 'origin/master' in remote_branches:
+          # Fall back on origin/master if it exits.
+          remote = 'origin'
+          upstream_branch = 'refs/heads/master'
+        elif 'origin/trunk' in remote_branches:
+          # Fall back on origin/trunk if it exists. Generally a shared
+          # git-svn clone
+          remote = 'origin'
+          upstream_branch = 'refs/heads/trunk'
+        else:
+          # Give up.
+          remote = None
+          upstream_branch = None
     return remote, upstream_branch
 
   @staticmethod
   def GetUpstreamBranch(cwd):
     """Gets the current branch's upstream branch."""
     remote, upstream_branch = GIT.FetchUpstreamTuple(cwd)
-    if remote != '.':
+    if remote != '.' and upstream_branch:
       upstream_branch = upstream_branch.replace('heads', 'remotes/' + remote)
     return upstream_branch
 
   @staticmethod
   def GenerateDiff(cwd, branch=None, branch_head='HEAD', full_move=False,
                    files=None):
     """Diffs against the upstream branch or optionally another branch.
 
     full_move means that move or copy operations should completely recreate the
     files, usually in the prospect to apply the patch for a try job."""
@@ skipping 541 matching lines @@
     if not SVN.current_version:
       SVN.current_version = SVN.Capture(['--version']).split()[2]
     current_version_list = map(only_int, SVN.current_version.split('.'))
     for min_ver in map(int, min_version.split('.')):
       ver = current_version_list.pop(0)
       if ver < min_ver:
         return (False, SVN.current_version)
       elif ver > min_ver:
         return (True, SVN.current_version)
     return (True, SVN.current_version)