Check for clang-format only if its files are present

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld and Gerrit."""
 
 from distutils.version import LooseVersion
@@ skipping 4422 matching lines @@
   diff_files = [x for x in diff_files if os.path.isfile(x)]
 
   clang_diff_files = [x for x in diff_files if MatchingFileType(x, CLANG_EXTS)]
   python_diff_files = [x for x in diff_files if MatchingFileType(x, ['.py'])]
   dart_diff_files = [x for x in diff_files if MatchingFileType(x, ['.dart'])]
   gn_diff_files = [x for x in diff_files if MatchingFileType(x, GN_EXTS)]
 
   top_dir = os.path.normpath(
       RunGit(["rev-parse", "--show-toplevel"]).rstrip('\n'))
 
-  # Locate the clang-format binary in the checkout
-  try:
-    clang_format_tool = clang_format.FindClangFormatToolInChromiumTree()
-  except clang_format.NotFoundError, e:
-    DieWithError(e)
-
   # Set to 2 to signal to CheckPatchFormatted() that this patch isn't
   # formatted. This is used to block during the presubmit.
   return_value = 0
 
   if clang_diff_files:
+    # Locate the clang-format binary in the checkout
+    try:
+      clang_format_tool = clang_format.FindClangFormatToolInChromiumTree()
+    except clang_format.NotFoundError, e:
+      DieWithError(e)
+
     if opts.full:
       cmd = [clang_format_tool]
       if not opts.dry_run and not opts.diff:
         cmd.append('-i')
       stdout = RunCommand(cmd + clang_diff_files, cwd=top_dir)
       if opts.diff:
         sys.stdout.write(stdout)
     else:
       env = os.environ.copy()
       env['PATH'] = str(os.path.dirname(clang_format_tool))
@@ skipping 164 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   setup_color.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)