[contrib] Prepare clang-format-diff for usage

contrib/devtools/README.md

@@ -7,6 +7,18 @@ clang-format.py
 
 A script to format cpp source code according to [.clang-format](../../src/.clang-format). This should only be applied to new files or files which are currently not actively developed on. Also, git subtrees are not subject to formatting.
 
+clang-format-diff.py
+===================
+
+A script to format unified git diffs according to [.clang-format](../../src/.clang-format).
+
+For instance, to format the last commit with 0 lines of context,
+the script should be called from the git root folder as follows.
+
+```
+git diff -U0 HEAD~1.. | ./contrib/devtools/clang-format-diff.py -p1 -i -v
+```
+
 fix-copyright-headers.py
 ========================
 

contrib/devtools/clang-format-diff.py

@@ -5,7 +5,52 @@
 #                     The LLVM Compiler Infrastructure
 #
 # This file is distributed under the University of Illinois Open Source
-# License. See LICENSE.TXT for details.
+# License.
+#
+#           ============================================================
+#
+# University of Illinois/NCSA
+# Open Source License
+#
+# Copyright (c) 2007-2015 University of Illinois at Urbana-Champaign.
+# All rights reserved.
+#
+# Developed by:
+#
+#     LLVM Team
+#
+#     University of Illinois at Urbana-Champaign
+#
+#     http://llvm.org
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal with
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+# of the Software, and to permit persons to whom the Software is furnished to do
+# so, subject to the following conditions:
+#
+#     * Redistributions of source code must retain the above copyright notice,
+#       this list of conditions and the following disclaimers.
+#
+#     * Redistributions in binary form must reproduce the above copyright notice,
+#       this list of conditions and the following disclaimers in the
+#       documentation and/or other materials provided with the distribution.
+#
+#     * Neither the names of the LLVM Team, University of Illinois at
+#       Urbana-Champaign, nor the names of its contributors may be used to
+#       endorse or promote products derived from this Software without specific
+#       prior written permission.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+# CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
+# SOFTWARE.
+#
+#           ============================================================
 #
 #===------------------------------------------------------------------------===#
 
@@ -56,10 +101,6 @@ def main():
                       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)')
   args = parser.parse_args()
 
   # Extract changed lines for each file.
@@ -101,8 +142,7 @@ def main():
     if args.sort_includes:
       command.append('-sort-includes')
     command.extend(lines)
-    if args.style:
-      command.extend(['-style', args.style])
+    command.extend(['-style=file', '-fallback-style=none'])
     p = subprocess.Popen(command, stdout=subprocess.PIPE,
                          stderr=None, stdin=subprocess.PIPE)
     stdout, stderr = p.communicate()