recipe engine: add remote_run command

recipe_engine/remote_run.py

Index: recipe_engine/remote_run.py
diff --git a/recipe_engine/remote_run.py b/recipe_engine/remote_run.py
new file mode 100644
index 0000000000000000000000000000000000000000..22f21feb46670ef6f20fed5a82f43b6de2adbd74
--- /dev/null
+++ b/recipe_engine/remote_run.py
@@ -0,0 +1,44 @@
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from __future__ import print_function
+
+import logging
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+
+from recipe_engine import fetch
+from recipe_engine import package
+
+
+def real_main(args):

[nodir, 2016/05/20 23:03:49]

a more elegant solution would be to use a context manager for creation and
deletion of temp dir

@contextlib.contextmanager
def init_workdir(args):
  # make temp dir
  try:
    yield
  finally:
    # delete temp dir

def main(args):
  with init_workdir(args):
    # code of real main

[Paweł Hajdan Jr., 2016/05/25 00:15:42]

Good point, done.

+  checkout_dir = os.path.join(args.workdir, 'checkout')
+  fetch.fetch_from_git(args.repository, args.revision, checkout_dir,
+                       allow_fetch=True)
+  recipes_cfg = package.ProtoFile(
+      package.InfraRepoConfig().to_recipes_cfg(checkout_dir))
+  cmd = [

[martiniss, 2016/05/20 22:11:34]

So, under the alternative logic, you would return from real_main here, and not
subprocess to run here. You would then go back to recipes.py, which would do the
regular fetch and call to run. So no need for a subprocess call, although the
control flow would be a bit strange.

I'm fine with this though.

+      sys.executable,
+      os.path.join(checkout_dir, recipes_cfg.read().recipes_path, 'recipes.py'),
+      'run'
+  ] + args.run_args
+  logging.info('Running %r', cmd)
+  return subprocess.call(cmd)
+
+
+def main(args):

[nodir, 2016/05/20 23:03:49]

document that args is result of parsing by remote_run parser defined in
recipes.py

[Paweł Hajdan Jr., 2016/05/25 00:15:41]

Whoa, does any other command do this? I'm not convinced a comment like that
would be useful.

+  workdir_tempdir = False
+  if not args.workdir:
+    workdir_tempdir = True
+    args.workdir = tempfile.mkdtemp(prefix='recipe_engine_remote_run_')
+    logging.info('Created temporary workdir %s', args.workdir)
+
+  try:
+    return real_main(args)
+  finally:
+    if workdir_tempdir:
+      shutil.rmtree(args.workdir, ignore_errors=True)