Add a cpplint preupload hook.

This runs cpplint.py over modified .cc and .h files before uploading
them to gerrit. This generally takes ~1-2 seconds based on my testing
and the longest one I've been able to find was ~10 seconds.

Test: PREUPLOAD_COMMIT=d9911eeca ./tools/cpplint_presubmit.py
Test: PREUPLOAD_COMMIT=405284789 ./tools/cpplint_presubmit.py
Test: PREUPLOAD_COMMIT=9763f2eb7 ./tools/cpplint_presubmit.py
Test: Manual

Bug: 35810246
Bug: 36855589

Change-Id: Ie0ed9136bdde15d78f2aa40c73fef97e12d12dda

2 files changed, 68 insertions, 0 deletions

diff --git a/PREUPLOAD.cfg b/PREUPLOAD.cfg
index cf1832beb4..0ed230c408 100644
--- a/PREUPLOAD.cfg
+++ b/PREUPLOAD.cfg
@@ -1,2 +1,3 @@
 [Hook Scripts]
 check_generated_files_up_to_date = tools/cpp-define-generator/presubmit-check-files-up-to-date
+check_cpplint_on_changed_files = tools/cpplint_presubmit.py
diff --git a/tools/cpplint_presubmit.py b/tools/cpplint_presubmit.py
new file mode 100755
index 0000000000..478151736f
--- /dev/null
+++ b/tools/cpplint_presubmit.py
@@ -0,0 +1,67 @@
+#!/usr/bin/python3
+#
+# Copyright 2017, The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# TODO We should unify this with build/Android.cpplint.mk.
+
+import os
+import pathlib
+import subprocess
+import sys
+
+IGNORED_FILES = {"runtime/elf.h", "runtime/openjdkjvmti/include/jvmti.h"}
+
+INTERESTING_SUFFIXES = {".h", ".cc"}
+
+CPPLINT_FLAGS = [
+    '--filter=-whitespace/line_length,-build/include,-readability/function,-readability/streams,-readability/todo,-runtime/references,-runtime/sizeof,-runtime/threadsafe_fn,-runtime/printf',
+    '--quiet',
+]
+
+def is_interesting(f):
+  """
+  Returns true if this is a file we want to run through cpplint before uploading. False otherwise.
+  """
+  path = pathlib.Path(f)
+  return f not in IGNORED_FILES and path.suffix in INTERESTING_SUFFIXES and path.exists()
+
+def get_changed_files(commit):
+  """
+  Gets the files changed in the given commit.
+  """
+  return subprocess.check_output(
+      ["git", 'diff-tree', '--no-commit-id', '--name-only', '-r', commit],
+      stderr=subprocess.STDOUT,
+      universal_newlines=True).split()
+
+def run_cpplint(files):
+  """
+  Runs cpplint on the given files.
+  """
+  if len(files) == 0:
+    return
+  sys.exit(subprocess.call(['tools/cpplint.py'] + CPPLINT_FLAGS + files))
+
+def main():
+  if 'PREUPLOAD_COMMIT' in os.environ:
+    commit = os.environ['PREUPLOAD_COMMIT']
+  else:
+    print("WARNING: Not running as a pre-upload hook. Assuming commit to check = 'HEAD'")
+    commit = "HEAD"
+  files_to_check = [f for f in get_changed_files(commit) if is_interesting(f)]
+  run_cpplint(files_to_check)
+
+if __name__ == '__main__':
+  main()