Cleanup chromite_wrapper.

The original design of this had some issues:

1) forced targets to be importable via 'buildbot.cbuildbot', rather
  than the proper/full 'chromite.buildbot.cbuildbot'.  Scripts worked
  around this, but it's an unwanted limitation.

2) That importation requirement means that within the chroot, we've
  had to export cros_sdk *and* cros_sdk.py in the PATH.  This is
  undesirable clutter, and introduces potential errors as scripts
  localize themselves to cros_sdk.py rather than invoking cros_sdk
  (the consumers should be agnostic to the language the tool is
  written in).

3) chromite_wrapper enforced assumptions about python namespace w/in
  the targets- specifically that 'main' must always be invokable
  without any arguments.  This limits refactoring/cleanup in chromite
  via having to support ancient API assumptions (api's that weren't
  public); modern chromite has repurposed main changing the prototype,
  and using it's own wrapper doing signal handler setup, and general
  framework behaviour.  Longer term, that 'main' functor is unlikely
  to even exist.  The strong coupling chromite_wrapper forced limits
  are refactoring possibilities.

4) In modern chromite, all user consumable tools are now required to
  exist w/in chromite/bin/, and be executable and invokable.  This is
  what we want going forward.

5) Implied we want chromite_wrapper used w/in the chroot; we don't,
  thus drop all CROS_WORKON_SRCROOT awareness.

6) Exposed a chromite_wrapper invokable (that didn't work) into the
  PATH outside the chroot; this is resolved via moving it into a
  support directory and repointing symlinks to it.

At this point, if it's working with a modern chromite checkout the
script is a simple execv pass thru.  If it isn't, then it will fallback
to the old import trickery.

This has been tested against R16, R17, R18, ToT, 0.11.241.B, factory-*,
basically all branches w/in chromite without issue.




git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@128555 0039d316-1c4b-4281-b951-d872f2087c98

Author: [email protected]

cbuildbot

@@ -1 +1 @@
-chromite_wrapper
+support/chromite_wrapper

chrome_set_ver

@@ -1 +1 @@
-chromite_wrapper
+support/chromite_wrapper

chromite_wrapper

@@ -1 +1 @@
-chromite_wrapper
+support/chromite_wrapper

cros_sdk

@@ -0,0 +1,89 @@
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Wrapper for chromite tools.
+
+The script is intend to be symlinked to any number of chromite tools, attempts
+to find the path for chromite, and hands off to the right tool via exec if
+possible.
+
+It is intended to used strictly outside of the chroot.
+
+If you're looking at a copy and want to know where the original looks at, look
+here:
+  http://git.chromium.org/gitweb/?p=chromite.git;a=blob;f=bin/chromite
+
+Since this script is _copied_, it should remain small and not use internal libs.
+
+"""
+
+import errno
+import os
+import sys
+
+# Due to historical reasons, and the fact depot_tools ToT is used by older
+# factory branches (lacking chromite script cleanups), note we have to
+# fallback to some odd import locations.  This is the only reason for the
+# fallback code- any/all new scripts symlinked to this script *must* exist
+# in chromite/bin/ .
+
+def _FindRoot(path):
+  """Find the root of a repo checkout"""
+  path = os.path.abspath(path)
+  while path != '/':
+    # Look for the chromite repository itself- it's always been at the root
+    # of a repo checkout.
+    if all(os.path.exists(os.path.join(path, x))
+           for x in ['.repo', 'chromite/.git']):
+      return path
+    path = os.path.dirname(path)
+  return None
+
+
+def _MissingErrorOut(target):
+  sys.stderr.write(
+"""ERROR: Couldn't find the chromite tool %s.
+
+Please change to a directory inside your Chromium OS source tree
+and retry.  If you need to setup a Chromium OS source tree, see
+  http://www.chromium.org/chromium-os/developer-guide
+""" % target)
+  return 127
+
+
+def main():
+  root = _FindRoot(os.getcwd())
+  target = os.path.basename(sys.argv[0])
+  if root is None:
+    return _MissingErrorOut(target)
+  
+  path = os.path.join(root, 'chromite/bin', target)
+  try:
+    os.execv(path, [path] + sys.argv[1:])
+  except EnvironmentError, e:
+    if e.errno not in (errno.ENOENT, errno.EPERM):
+      raise
+
+  # Reaching here means it's either a bad target, or we're working against
+  # an old (pre 6be2efcf5bb575b03862113eec097c44d8d7f93e) revision of
+  # chromite.  Fallback to trying to import it; this code works at least as
+  # far back as branch 0.11.241.B; likely further.
+  
+  if target == 'cbuildbot':
+    target = 'chromite.buildbot.cbuildbot'
+  else:
+    target = 'chromite.bin.%s' % (target,)
+
+  # Adjust the path importation so we can import our our target.
+  sys.path.insert(0, root)
+
+  try:
+    module = __import__(target, fromlist=['main'])
+  except ImportError:
+    return _MissingErrorOut(target)
+  return module.main()
+
+if __name__ == '__main__':
+  sys.exit(main())