Don't clobber the PATH environment variable when running git commit.

testing_support/git/repo.py

 # 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.
 
 import atexit
 import collections
 import datetime
 import os
 import shutil
 import subprocess
@@ skipping 88 matching lines @@
 
     if commit.parents:
       parents = list(commit.parents)
       self.git('checkout', '--detach', '-q', self[parents[0]])
       if len(parents) > 1:
         self.git('merge', '--no-commit', '-q', *[self[x] for x in parents[1:]])
     else:
       self.git('checkout', '--orphan', 'root_%s' % commit.name)
       self.git('rm', '-rf', '.')
 
-    env = self.get_git_commit_env(commit_data)
+    env = os.environ.copy()
+    env.update(self.get_git_commit_env(commit_data))
 
     for fname, file_data in commit_data.iteritems():
       deleted = False
       if 'data' in file_data:
         data = file_data.get('data')
         if data is None:
           deleted = True
           self.git('rm', fname)
         else:
           path = os.path.join(self.repo_path, fname)
@@ skipping 40 matching lines @@
     assert self.repo_path is not None
     try:
       with open(os.devnull, 'wb') as devnull:
         output = subprocess.check_output(
           ('git',) + args, cwd=self.repo_path, stderr=devnull, **kwargs)
       return self.COMMAND_OUTPUT(0, output)
     except subprocess.CalledProcessError as e:
       return self.COMMAND_OUTPUT(e.returncode, e.output)
 
   def git_commit(self, message):
-    return self.git('commit', '-am', message, env=self.get_git_commit_env())
+    env = os.environ.copy()
+    env.update(self.get_git_commit_env())
+    return self.git('commit', '-am', message, env=env)
 
   def nuke(self):
     """Obliterates the git repo on disk.
 
     Causes this GitRepo to be unusable.
     """
     shutil.rmtree(self.repo_path)
     self.repo_path = None
 
   def run(self, fn, *args, **kwargs):
@@ skipping 51 matching lines @@
       else:
         assert current is not None
         hash_to_msg[current] = line
         ret.add_partial(line)
         for parent in parents:
           ret.add_partial(line, hash_to_msg[parent])
         current = None
         parents = []
     assert current is None
     return ret