diff --git a/clang/tools/clang-format/git-clang-format b/clang/tools/clang-format/git-clang-format
--- a/clang/tools/clang-format/git-clang-format
+++ b/clang/tools/clang-format/git-clang-format
@@ -99,6 +99,8 @@
                  help='default commit to use if none is specified'),
   p.add_argument('--diff', action='store_true',
                  help='print a diff instead of applying the changes')
+  p.add_argument('--diffstat', action='store_true',
+                 help='print a diffstat instead of applying the changes')
   p.add_argument('--extensions',
                  default=config.get('clangformat.extensions',
                                     default_extensions),
@@ -176,6 +178,8 @@
       print('clang-format did not modify any files')
   elif opts.diff:
     print_diff(old_tree, new_tree)
+  elif opts.diffstat:
+    print_diffstat(old_tree, new_tree)
   else:
     changed_files = apply_changes(old_tree, new_tree, force=opts.force,
                                   patch_mode=opts.patch)
@@ -506,6 +510,17 @@
   subprocess.check_call(['git', 'diff', '--diff-filter=M', old_tree, new_tree,
                          '--'])
 
+def print_diffstat(old_tree, new_tree):
+  """Print the diffstat between the two trees to stdout."""
+  # We use the porcelain 'diff' and not plumbing 'diff-tree' because the output
+  # is expected to be viewed by the user, and only the former does nice things
+  # like color and pagination.
+  #
+  # We also only print modified files since `new_tree` only contains the files
+  # that were modified, so unmodified files would show as deleted without the
+  # filter.
+  subprocess.check_call(['git', 'diff', '--diff-filter=M', '--stat', old_tree, new_tree,
+                         '--'])
 
 def apply_changes(old_tree, new_tree, force=False, patch_mode=False):
   """Apply the changes in `new_tree` to the working directory.