clang-format: Use git-ls-tree to get file mode in diff mode

[lhchavez]

Summary

If a file has been renamed/deleted from the filesystem and --diff mode
with two commits is active, attempting to get the file's mode will fail.
This change uses git-ls-tree instead to get the correct permissions for
the given revision.

[lodato]

Thanks for the fix!

cfe/trunk/tools/clang-format/git-clang-format

 
 def run_clang_format_and_save_to_tree(changed_lines, revision=None,
                                       binary='clang-format', style=None):
   """Run clang-format on each file and save the result to a git tree.
 
   Returns the object ID (SHA-1) of the created tree."""
   def index_info_generator():
     for filename, line_ranges in changed_lines.iteritems():
+      if revision:
+        git_metadata_cmd = ['git', 'ls-tree',
+                            '%s:%s' % (revision, os.path.dirname(filename)),
+                            os.path.basename(filename)]
+        git_metadata = subprocess.Popen(git_metadata_cmd, stdin=subprocess.PIPE,
+                                        stdout=subprocess.PIPE)
+        stdout = git_metadata.communicate()[0]
+        mode = oct(int(stdout.split()[0], 8))
+      else:
         mode = oct(os.stat(filename).st_mode)
       blob_id = clang_format_to_blob(filename, line_ranges,
                                      revision=revision,
                                      binary=binary,
                                      style=style)
       yield '%s %s\t%s' % (mode, blob_id, filename)
   return create_tree(index_info_generator(), '--index-info')