Accommodate git repositories when re-rooting the cpplint invocation.

runtime/PRESUBMIT.py

Index: runtime/PRESUBMIT.py
diff --git a/runtime/PRESUBMIT.py b/runtime/PRESUBMIT.py
index c3bf724daae845202487ebaa656701c66ce5d2f9..7c76202e446caf4f6412bd6b34c4a15d8f731f51 100644
--- a/runtime/PRESUBMIT.py
+++ b/runtime/PRESUBMIT.py
@@ -2,8 +2,54 @@
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-import cpplint
 import os
+import cpplint
+
+
+class PathHackException(Exception):
+  def __init__(self, error_msg):
+    self.error_msg = error_msg
+
+  def __str__(self):
+    return repr(self.error_msg)
+
+
+def TrySvnPathHack(parent_path):
+  orig_path = os.path.join(parent_path, '.svn')
+  renamed_path = os.path.join(parent_path, '.svn_orig')
+  if os.path.exists(renamed_path):
+    error_msg = '".svn_orig" exists in presubmit parent directory('
+    error_msg += parent_path
+    error_msg += '). Consider renaming it manually to ".svn".'
+    raise PathHackException(error_msg)
+  if os.path.exists(orig_path):
+    # Make the parent SVN directory non-discoverable by cpplint to get
+    # the correct header guard checks. This is needed if using all Dart
+    # checkout.
+    os.rename(orig_path, renamed_path)
+    return lambda: os.rename(renamed_path, orig_path)
+
+
+def TryGitPathHack(filename, parent_path):
+  def CommonSubdirectory(parent, child):
+    while len(child) > len(parent):
+      child, tail = os.path.split(child)
+      if child == parent:
+        return os.path.join(parent, tail)
+  if os.path.exists(os.path.join(parent_path, '.git')):
+    runtime_path = CommonSubdirectory(parent_path, filename)
+    if runtime_path is not None:
+      fake_svn_path = os.path.join(runtime_path, '.svn')
+      if os.path.exists(fake_svn_path):
+        error_msg = '".svn" exists in presubmit parent subdirectory('
+        error_msg += fake_svn_path
+        error_msg += '). Consider removing it manually.'
+        raise PathHackException(error_msg)
+      # Deposit a file named ".svn" in the runtime directory to fool
+      # cpplint into thinking it is the source root.
+      open(fake_svn_path, 'w').close()
+      return lambda: os.remove(fake_svn_path)
+
 
 def RunLint(input_api, output_api):
   result = []
@@ -12,35 +58,28 @@ def RunLint(input_api, output_api):
   for svn_file in input_api.AffectedTextFiles():
     filename = svn_file.AbsoluteLocalPath()
     if filename.endswith('.cc') or filename.endswith('.h'):
-      hacked_parent_svn = 0
-      if filename.endswith('.h'):
-        parent_path = os.path.dirname(input_api.PresubmitLocalPath())
-        orig_path = os.path.join(parent_path, '.svn')
-        renamed_path = os.path.join(parent_path, '.svn_orig')
-        if (os.path.exists(renamed_path)):
-          error_msg = '".svn_orig" exists in presubmit parent directory('
-          error_msg += parent_path
-          error_msg += '). Consider renaming it manually to ".svn".'
-          result = [output_api.PresubmitError(error_msg)]
-          return result
-        if (os.path.exists(orig_path)):
-          # Make the parent SVN directory non-discoverable by cpplint to get
-          # the correct header guard checks. This is needed if using all Dart
-          # checkout.
-          os.rename(orig_path, renamed_path)
-          hacked_parent_svn = 1
+      cleanup = None
+      parent_path = os.path.dirname(input_api.PresubmitLocalPath())
+      try:
+        if filename.endswith('.h'):
+          cleanup = TrySvnPathHack(parent_path)
+          if cleanup is None:
+            cleanup = TryGitPathHack(filename, parent_path)
+      except PathHackException, exception:
+        return [output_api.PresubmitError(str(exception))]
       # Run cpplint on the file.
       cpplint.ProcessFile(filename, 1)
-      if hacked_parent_svn != 0:
-        # Undo hacks from above: Restore the original name.
-        os.rename(renamed_path, orig_path)
+      if cleanup is not None:
+        cleanup()
   # Report a presubmit error if any of the files had an error.
   if cpplint._cpplint_state.error_count > 0:
     result = [output_api.PresubmitError('Failed cpplint check.')]
   return result
 
+
 def CheckChangeOnUpload(input_api, output_api):
   return RunLint(input_api, output_api)
 
+
 def CheckChangeOnCommit(input_api, output_api):
   return RunLint(input_api, output_api)