Gerrit git cl: allow overriding GERRIT_SQUASH_UPLOADS in git config.

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld and Gerrit."""
 
 from distutils.version import LooseVersion
@@ skipping 2817 matching lines @@
   SetProperty('cpplint-ignore-regex', 'LINT_IGNORE_REGEX', unset_error_ok=True)
   SetProperty('project', 'PROJECT', unset_error_ok=True)
   SetProperty('pending-ref-prefix', 'PENDING_REF_PREFIX', unset_error_ok=True)
   SetProperty('run-post-upload-hook', 'RUN_POST_UPLOAD_HOOK',
               unset_error_ok=True)
 
   if 'GERRIT_HOST' in keyvals:
     RunGit(['config', 'gerrit.host', keyvals['GERRIT_HOST']])
 
   if 'GERRIT_SQUASH_UPLOADS' in keyvals:
-    RunGit(['config', 'gerrit.squash-uploads',
-            keyvals['GERRIT_SQUASH_UPLOADS']])
+    cur = RunGit(['config', '--bool', 'gerrit.squash-uploads'], error_ok=True)
+    if not cur:  # Set the value only if it wasn't set by the user manually.
+      RunGit(['config', 'gerrit.squash-uploads',
+              keyvals['GERRIT_SQUASH_UPLOADS']])
 
   if 'GERRIT_SKIP_ENSURE_AUTHENTICATED' in keyvals:
     RunGit(['config', 'gerrit.skip-ensure-authenticated',
             keyvals['GERRIT_SKIP_ENSURE_AUTHENTICATED']])
 
   if 'PUSH_URL_CONFIG' in keyvals and 'ORIGIN_URL_CONFIG' in keyvals:
     #should be of the form
     #PUSH_URL_CONFIG: url.ssh://gitrw.chromium.org.pushinsteadof
     #ORIGIN_URL_CONFIG: http://src.chromium.org/git
     RunGit(['config', keyvals['PUSH_URL_CONFIG'],
@@ skipping 2183 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   setup_color.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)