recipes/recipe_modules/gclient/resources/diff_deps.py

#!/usr/bin/env python
import os
import subprocess
import sys

if '@' in os.environ.get('GCLIENT_URL'):
  ref = os.environ.get('GCLIENT_URL').split('@')[-1]
else:
  sys.exit(0)

diff = subprocess.check_output("git diff --cached --name-only %s" % ref, shell=True)

dep_path = os.environ.get('GCLIENT_DEP_PATH', '')
for line in diff.splitlines():
  if line:
    print(os.path.join(dep_path,  line))