clang-format-diff: Replace hard-code default for clang-format binary with flag.

Patch by Kwasi Mensah, thank you.

git-svn-id: svn://svn.chromium.org/llvm-project/cfe/trunk/tools/clang-format@258328 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
diff --git a/clang-format-diff.py b/clang-format-diff.py
index 9e02bb0..5e728f5 100755
--- a/clang-format-diff.py
+++ b/clang-format-diff.py
@@ -31,10 +31,6 @@
 import sys
 
 
-# Change this to the full path if clang-format is not on the path.
-binary = 'clang-format'
-
-
 def main():
   parser = argparse.ArgumentParser(description=
                                    'Reformat changed lines in diff. Without -i '
@@ -56,10 +52,11 @@
                       help='let clang-format sort include blocks')
   parser.add_argument('-v', '--verbose', action='store_true',
                       help='be more verbose, ineffective without -i')
-  parser.add_argument(
-      '-style',
-      help=
-      'formatting style to apply (LLVM, Google, Chromium, Mozilla, WebKit)')
+  parser.add_argument('-style',
+                      help='formatting style to apply (LLVM, Google, Chromium, '
+                      'Mozilla, WebKit)')
+  parser.add_argument('-binary', default='clang-format',
+                      help='location of binary to use for clang-format')
   args = parser.parse_args()
 
   # Extract changed lines for each file.
@@ -95,7 +92,7 @@
   for filename, lines in lines_by_file.iteritems():
     if args.i and args.verbose:
       print 'Formatting', filename
-    command = [binary, filename]
+    command = [args.binary, filename]
     if args.i:
       command.append('-i')
     if args.sort_includes: