Add recipes config & temp hello_world recipe

The non-generated files are:
- infra/config/recipes.cfg
- recipes/recipes.py
- recipes/recipes/hello_world.py
- .gitignore

Then ran command to generate and test everything:
$ python2.7 ./recipes/recipes.py test train

Google-Bug-Id: b/238869100
Change-Id: Ie6e987b87c85ba173b036bf1db74b76b05f22f19
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6789a29
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+**/.recipe_deps
\ No newline at end of file
diff --git a/infra/config/recipes.cfg b/infra/config/recipes.cfg
new file mode 100644
index 0000000..1ea176d
--- /dev/null
+++ b/infra/config/recipes.cfg
@@ -0,0 +1,13 @@
+{
+  "api_version": 2,
+  "repo_name": "gerrit",
+  "canonical_repo_url": "https://gerrit.googlesource.com/luci-config.git",
+  "deps": {
+    "recipe_engine": {
+      "branch": "refs/heads/main",
+      "revision": "6a02d019c4b24e4412cc40003c4397320be41cae",
+      "url": "https://chromium.googlesource.com/infra/luci/recipes-py.git"
+    }
+  },
+  "recipes_path": "recipes"
+}
\ No newline at end of file
diff --git a/recipes/README.recipes.md b/recipes/README.recipes.md
new file mode 100644
index 0000000..40c7a41
--- /dev/null
+++ b/recipes/README.recipes.md
@@ -0,0 +1,17 @@
+<!--- AUTOGENERATED BY `./recipes.py test train` -->
+# Repo documentation for [gerrit](https://gerrit.googlesource.com/luci-config.git)
+## Table of Contents
+
+**[Recipes](#Recipes)**
+  * [hello_world](#recipes-hello_world)
+## Recipes
+
+### *recipes* / [hello\_world](/recipes/recipes/hello_world.py)
+
+[DEPS](/recipes/recipes/hello_world.py#7): [recipe\_engine/step][recipe_engine/recipe_modules/step]
+
+PYTHON_VERSION_COMPATIBILITY: PY2
+
+&mdash; **def [RunSteps](/recipes/recipes/hello_world.py#11)(api):**
+
+[recipe_engine/recipe_modules/step]: https://chromium.googlesource.com/infra/luci/recipes-py.git/+/6a02d019c4b24e4412cc40003c4397320be41cae/README.recipes.md#recipe_modules-step
diff --git a/recipes/recipes.py b/recipes/recipes.py
new file mode 100755
index 0000000..e21456b
--- /dev/null
+++ b/recipes/recipes.py
@@ -0,0 +1,237 @@
+#!/bin/sh
+# We want to run python in unbuffered mode; however shebangs on linux grab the
+# entire rest of the shebang line as a single argument, leading to errors like:
+#
+#   /usr/bin/env: 'python -u': No such file or directory
+#
+# This little shell hack is a triple-quoted noop in python, but in sh it
+# evaluates to re-exec'ing this script in unbuffered mode.
+''''exec python -u -- "$0" ${1+"$@"} # '''
+# vi: syntax=python
+
+# Copyright 2017 The LUCI Authors. All rights reserved.
+# Use of this source code is governed under the Apache License, Version 2.0
+# that can be found in the LICENSE file.
+
+"""Bootstrap script to clone and forward to the recipe engine tool.
+
+*******************
+** DO NOT MODIFY **
+*******************
+
+This is a copy of https://chromium.googlesource.com/infra/luci/recipes-py/+/master/recipes.py.
+To fix bugs, fix in the googlesource repo then run the autoroller.
+"""
+
+# pylint: disable=wrong-import-position
+import argparse
+import json
+import logging
+import os
+import subprocess
+import sys
+import urlparse
+
+from collections import namedtuple
+
+# The dependency entry for the recipe_engine in the client repo's recipes.cfg
+#
+# url (str) - the url to the engine repo we want to use.
+# revision (str) - the git revision for the engine to get.
+# branch (str) - the branch to fetch for the engine as an absolute ref (e.g.
+#   refs/heads/master)
+EngineDep = namedtuple('EngineDep',
+                       'url revision branch')
+
+
+class MalformedRecipesCfg(Exception):
+  def __init__(self, msg, path):
+    super(MalformedRecipesCfg, self).__init__('malformed recipes.cfg: %s: %r'
+                                              % (msg, path))
+
+
+def parse(repo_root, recipes_cfg_path):
+  """Parse is a lightweight a recipes.cfg file parser.
+
+  Args:
+    repo_root (str) - native path to the root of the repo we're trying to run
+      recipes for.
+    recipes_cfg_path (str) - native path to the recipes.cfg file to process.
+
+  Returns (as tuple):
+    engine_dep (EngineDep|None): The recipe_engine dependency, or None, if the
+      current repo IS the recipe_engine.
+    recipes_path (str) - native path to where the recipes live inside of the
+      current repo (i.e. the folder containing `recipes/` and/or
+      `recipe_modules`)
+  """
+  with open(recipes_cfg_path, 'rU') as fh:
+    pb = json.load(fh)
+
+  try:
+    if pb['api_version'] != 2:
+      raise MalformedRecipesCfg('unknown version %d' % pb['api_version'],
+                                recipes_cfg_path)
+
+    # If we're running ./recipes.py from the recipe_engine repo itself, then
+    # return None to signal that there's no EngineDep.
+    repo_name = pb.get('repo_name')
+    if not repo_name:
+      repo_name = pb['project_id']
+    if repo_name == 'recipe_engine':
+      return None, pb.get('recipes_path', '')
+
+    engine = pb['deps']['recipe_engine']
+
+    if 'url' not in engine:
+      raise MalformedRecipesCfg(
+        'Required field "url" in dependency "recipe_engine" not found',
+        recipes_cfg_path)
+
+    engine.setdefault('revision', '')
+    engine.setdefault('branch', 'refs/heads/master')
+    recipes_path = pb.get('recipes_path', '')
+
+    # TODO(iannucci): only support absolute refs
+    if not engine['branch'].startswith('refs/'):
+      engine['branch'] = 'refs/heads/' + engine['branch']
+
+    recipes_path = os.path.join(
+      repo_root, recipes_path.replace('/', os.path.sep))
+    return EngineDep(**engine), recipes_path
+  except KeyError as ex:
+    raise MalformedRecipesCfg(ex.message, recipes_cfg_path)
+
+
+_BAT = '.bat' if sys.platform.startswith(('win', 'cygwin')) else ''
+GIT = 'git' + _BAT
+VPYTHON = 'vpython' + _BAT
+CIPD = 'cipd' + _BAT
+REQUIRED_BINARIES = {GIT, VPYTHON, CIPD}
+
+
+def _is_executable(path):
+  return os.path.isfile(path) and os.access(path, os.X_OK)
+
+# TODO: Use shutil.which once we switch to Python3.
+def _is_on_path(basename):
+  for path in os.environ['PATH'].split(os.pathsep):
+    full_path = os.path.join(path, basename)
+    if _is_executable(full_path):
+      return True
+  return False
+
+
+def _subprocess_call(argv, **kwargs):
+  logging.info('Running %r', argv)
+  return subprocess.call(argv, **kwargs)
+
+
+def _git_check_call(argv, **kwargs):
+  argv = [GIT]+argv
+  logging.info('Running %r', argv)
+  subprocess.check_call(argv, **kwargs)
+
+
+def _git_output(argv, **kwargs):
+  argv = [GIT]+argv
+  logging.info('Running %r', argv)
+  return subprocess.check_output(argv, **kwargs)
+
+
+def parse_args(argv):
+  """This extracts a subset of the arguments that this bootstrap script cares
+  about. Currently this consists of:
+    * an override for the recipe engine in the form of `-O recipe_engine=/path`
+    * the --package option.
+  """
+  PREFIX = 'recipe_engine='
+
+  p = argparse.ArgumentParser(add_help=False)
+  p.add_argument('-O', '--project-override', action='append')
+  p.add_argument('--package', type=os.path.abspath)
+  args, _ = p.parse_known_args(argv)
+  for override in args.project_override or ():
+    if override.startswith(PREFIX):
+      return override[len(PREFIX):], args.package
+  return None, args.package
+
+
+def checkout_engine(engine_path, repo_root, recipes_cfg_path):
+  dep, recipes_path = parse(repo_root, recipes_cfg_path)
+  if dep is None:
+    # we're running from the engine repo already!
+    return os.path.join(repo_root, recipes_path)
+
+  url = dep.url
+
+  if not engine_path and url.startswith('file://'):
+    engine_path = urlparse.urlparse(url).path
+
+  if not engine_path:
+    revision = dep.revision
+    branch = dep.branch
+
+    # Ensure that we have the recipe engine cloned.
+    engine_path = os.path.join(recipes_path, '.recipe_deps', 'recipe_engine')
+
+    with open(os.devnull, 'w') as NUL:
+      # Note: this logic mirrors the logic in recipe_engine/fetch.py
+      _git_check_call(['init', engine_path], stdout=NUL)
+
+      try:
+        _git_check_call(['rev-parse', '--verify', '%s^{commit}' % revision],
+                        cwd=engine_path, stdout=NUL, stderr=NUL)
+      except subprocess.CalledProcessError:
+        _git_check_call(['fetch', url, branch], cwd=engine_path, stdout=NUL,
+                        stderr=NUL)
+
+    try:
+      _git_check_call(['diff', '--quiet', revision], cwd=engine_path)
+    except subprocess.CalledProcessError:
+      _git_check_call(['reset', '-q', '--hard', revision], cwd=engine_path)
+
+    # If the engine has refactored/moved modules we need to clean all .pyc files
+    # or things will get squirrely.
+    _git_check_call(['clean', '-qxf'], cwd=engine_path)
+
+  return engine_path
+
+
+def main():
+  for required_binary in REQUIRED_BINARIES:
+    if not _is_on_path(required_binary):
+      return 'Required binary is not found on PATH: %s' % required_binary
+
+  if '--verbose' in sys.argv:
+    logging.getLogger().setLevel(logging.INFO)
+
+  args = sys.argv[1:]
+  engine_override, recipes_cfg_path = parse_args(args)
+
+  if recipes_cfg_path:
+    # calculate repo_root from recipes_cfg_path
+    repo_root = os.path.dirname(
+      os.path.dirname(
+        os.path.dirname(recipes_cfg_path)))
+  else:
+    # find repo_root with git and calculate recipes_cfg_path
+    repo_root = (_git_output(
+      ['rev-parse', '--show-toplevel'],
+      cwd=os.path.abspath(os.path.dirname(__file__))).strip())
+    repo_root = os.path.abspath(repo_root)
+    recipes_cfg_path = os.path.join(repo_root, 'infra', 'config', 'recipes.cfg')
+    args = ['--package', recipes_cfg_path] + args
+
+  engine_path = checkout_engine(engine_override, repo_root, recipes_cfg_path)
+
+  try:
+    return _subprocess_call([
+        VPYTHON, '-u',
+        os.path.join(engine_path, 'recipe_engine', 'main.py')] + args)
+  except KeyboardInterrupt:
+    return 1
+
+
+if __name__ == '__main__':
+  sys.exit(main())
diff --git a/recipes/recipes/hello_world.expected/basic.json b/recipes/recipes/hello_world.expected/basic.json
new file mode 100644
index 0000000..b692cbb
--- /dev/null
+++ b/recipes/recipes/hello_world.expected/basic.json
@@ -0,0 +1,9 @@
+[
+  {
+    "cmd": [],
+    "name": "Hello world"
+  },
+  {
+    "name": "$result"
+  }
+]
\ No newline at end of file
diff --git a/recipes/recipes/hello_world.py b/recipes/recipes/hello_world.py
new file mode 100644
index 0000000..799add8
--- /dev/null
+++ b/recipes/recipes/hello_world.py
@@ -0,0 +1,18 @@
+# Enumerates the recipe modules that this recipe uses.
+#
+# "recipe_engine" is the "repo_name" for the recipes-py repo, and "step"
+# is the name of the "step" recipe module within that repo. The
+# "recipe_engine/step" module will be the most frequently-used module in your
+# recipes as it allows you to run executables within your build.
+DEPS = [
+  "recipe_engine/step",
+]
+
+def RunSteps(api):
+  # Creates an 'empty' (i.e. no-op) step in the UI with the name "Hello world".
+  api.step.empty("Hello world")
+
+def GenTests(api):
+  # Tells the recipe engine to generate an expectation file (JSON simulation
+  # output) for this recipe when it is run without any input properties.
+  yield api.test("basic")