Make auto-svn also configure the current svn branch (if any).

git_auto_svn.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 """Performs all git-svn setup steps necessary for 'git svn dcommit' to work.
 
 Assumes that trunk of the svn remote maps to master of the git remote.
 
 Example:
 git clone https://chromium.googlesource.com/chromium/tools/depot_tools
 cd depot_tools
 git auto-svn
 """
 
 import argparse
 import os
 import sys
 import urlparse
 
 import subprocess2
 
 from git_common import run as run_git
 from git_common import run_stream_with_retcode as run_git_stream_with_retcode
-from git_common import set_config, root, ROOT
+from git_common import set_config, root, ROOT, current_branch
+from git_common import upstream as get_upstream
 from git_footers import get_footer_svn_id
 
 
 SVN_EXE = ROOT+'\\svn.bat' if sys.platform.startswith('win') else 'svn'
 
 
 def run_svn(*cmd, **kwargs):
   """Runs an svn command.
 
   Returns (stdout, stderr) as a pair of strings.
@@ skipping 14 matching lines @@
   return ret, err
 
 
 def main(argv):
   # No command line flags. Just use the parser to prevent people from trying
   # to pass flags that don't do anything, and to provide 'usage'.
   parser = argparse.ArgumentParser(
       description='Automatically set up git-svn for a repo mirrored from svn.')
   parser.parse_args(argv)
 
-  upstream = root()
+  upstreams = []
+  # Always configure the upstream trunk.
+  upstreams.append(root())
+  # Optionally configure whatever upstream branch might be currently checked
+  # out. This is needed for work on svn-based branches, otherwise git-svn gets
+  # very confused and tries to relate branch commits back to trunk, making a big
+  # mess of the codereview patches, and generating all kinds of spurious errors
+  # about the repo being in some sort of bad state.
+  curr_upstream = get_upstream(current_branch())
+  # There will be no upstream if the checkout is in detached HEAD.
+  if curr_upstream:
+    upstreams.append(curr_upstream)
+  for upstream in upstreams:
+    config_svn(upstream)
+  return 0
+
+
+def config_svn(upstream):
   svn_id = get_footer_svn_id(upstream)
   assert svn_id, 'No valid git-svn-id footer found on %s.' % upstream
   print 'Found git-svn-id footer %s on %s' % (svn_id, upstream)
 
   parsed_svn = urlparse.urlparse(svn_id)
   path_components = parsed_svn.path.split('/')
   svn_repo = None
   svn_path = None
   for i in xrange(len(path_components)):
     try:
       maybe_repo = '%s://%s%s' % (
           parsed_svn.scheme, parsed_svn.netloc, '/'.join(path_components[:i+1]))
       print 'Checking ', maybe_repo
       run_svn('info', maybe_repo)
       svn_repo = maybe_repo
       svn_path = '/'.join(path_components[i+1:])
       break
     except subprocess2.CalledProcessError, e:
       if 'E170001' in str(e):
         print 'Authentication failed:'
         print e
         print ('Try running "svn ls %s" with the password'
                ' from https://chromium-access.appspot.com' % maybe_repo)
         print
       continue
   assert svn_repo is not None, 'Unable to find svn repo for %s' % svn_id
   print 'Found upstream svn repo %s and path %s' % (svn_repo, svn_path)
 
-  set_config('svn-remote.svn.url', svn_repo)
-  set_config('svn-remote.svn.fetch',
-             '%s:refs/remotes/%s' % (svn_path, upstream))
+  run_git('config', '--local', '--replace-all', 'svn-remote.svn.url', svn_repo)
+  run_git('config', '--local', '--replace-all', 'svn-remote.svn.fetch',
+          '%s:refs/remotes/%s' % (svn_path, upstream),
+          'refs/remotes/%s$' % upstream)
   print 'Configured metadata, running "git svn fetch". This may take some time.'
   with run_git_stream_with_retcode('svn', 'fetch') as stdout:
     for line in stdout.xreadlines():
       print line.strip()
-  return 0
 
 
 if __name__ == '__main__':
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)