Better error checking in git freeze

tests/git_common_test.py

 #!/usr/bin/env python
 # Copyright 2013 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.
 
 """Unit tests for git_common.py"""
 
 import binascii
 import collections
 import os
@@ skipping 841 matching lines @@
       self.repo.git('add', 'bad_merge')
       self.repo.git('commit', '-m', 'bad_merge_d')
 
       self.repo.git('merge', 'bad_merge_branch')
 
       _, err = self.repo.capture_stdio(self.gc.freeze)
       self.assertIn('Cannot freeze unmerged changes', err)
 
     self.repo.run(inner)
 
+  def testAddError(self):
+    def inner():
+      self.repo.git('checkout', '-b', 'unreadable_file_branch')
+      with open('bad_file', 'w') as f:
+        f.write('some text')
+      os.chmod('bad_file', 0111)
+      ret = self.repo.run(self.gc.freeze)
+      self.assertIn('Failed to index some unindexed files.', ret)
+
+    self.repo.run(inner)
+
 
 class GitMakeWorkdir(git_test_utils.GitRepoReadOnlyTestBase, GitCommonTestBase):
   def setUp(self):
     self._tempdir = tempfile.mkdtemp()
 
   def tearDown(self):
     shutil.rmtree(self._tempdir)
 
   REPO_SCHEMA = """
   A
@@ skipping 40 matching lines @@
                       self.repo.show_commit('A', format_string='%cn %ci'))
     self.assertEquals('Author McAuthorly 1970-01-03 00:00:00 +0000',
                       self.repo.show_commit('B', format_string='%an %ai'))
     self.assertEquals('Charles Committish 1970-01-04 00:00:00 +0000',
                       self.repo.show_commit('B', format_string='%cn %ci'))
 
 
 if __name__ == '__main__':
   sys.exit(coverage_utils.covered_main(
     os.path.join(DEPOT_TOOLS_ROOT, 'git_common.py')))