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
@@ -198,9 +198,9 @@
     return 0
 
   if opts.diff:
-    print_diff(old_tree, new_tree)
+    return print_diff(old_tree, new_tree)
   elif opts.diffstat:
-    print_diffstat(old_tree, new_tree)
+    return print_diffstat(old_tree, new_tree)
   else:
     changed_files = apply_changes(old_tree, new_tree, force=opts.force,
                                   patch_mode=opts.patch)
@@ -209,7 +209,7 @@
       for filename in changed_files:
         print('    %s' % filename)
 
-  return 1
+    return 1
 
 
 def load_git_config(non_string_options=None):
@@ -536,8 +536,8 @@
   # 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', old_tree, new_tree,
-                         '--'])
+  subprocess.check_call(['git', 'diff', '--diff-filter=M',
+                        old_tree, new_tree, '--exit-code', '--'])
 
 def print_diffstat(old_tree, new_tree):
   """Print the diffstat between the two trees to stdout."""
@@ -548,7 +548,13 @@
   # 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,
+  subprocess.check_call(['git',
+                         'diff',
+                         '--diff-filter=M',
+                         '--stat',
+                         old_tree,
+                         new_tree,
+                         '--exit-code',
                          '--'])
 
 def apply_changes(old_tree, new_tree, force=False, patch_mode=False):