Add a presubmit check to prevent committing .rej/.orig patch files

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 6ab44910877fbd05cbf94e12fb0af77f00cf777f..f16d273ab1d4f0e7caefc583f0e2dd3fc12dd973 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -669,6 +669,7 @@ def _CommonChecks(input_api, output_api):
   results.extend(_CheckNoAuraWindowPropertyHInHeaders(input_api, output_api))
   results.extend(_CheckIncludeOrder(input_api, output_api))
   results.extend(_CheckForVersionControlConflicts(input_api, output_api))
+  results.extend(_CheckPatchFiles(input_api, output_api))
 
   if any('PRESUBMIT.py' == f.LocalPath() for f in input_api.AffectedFiles()):
     results.extend(input_api.canned_checks.RunUnitTestsInDirectory(
@@ -752,6 +753,16 @@ def _CheckAuthorizedAuthor(input_api, output_api):
   return []
 
 
+def _CheckPatchFiles(input_api, output_api):
+  problems = [f.LocalPath() for f in input_api.AffectedFiles()

[M-A Ruel, 2012/12/05 19:39:22]

In theory, you should put this one at +4 too on next line

[enne (OOO), 2012/12/05 19:46:44]

Oh? Are you suggesting to linebreak after the bracket? (Although in that case,
wouldn't it just be +2 indent?)

I'm happy to change it to whatever you want, I just don't quite follow. 
\noideadog{enne formatting Python code}

[M-A Ruel, 2012/12/05 19:51:08]

Actually, you are right it'd be +2, don't bother.

+      if f.LocalPath().endswith(('.orig', '.rej'))]
+  if problems:
+    return [output_api.PresubmitError(
+        "Don't commit .rej and .orig files.", problems)]
+  else:
+    return []
+
+
 def CheckChangeOnUpload(input_api, output_api):
   results = []
   results.extend(_CommonChecks(input_api, output_api))