[cr tool] Adding the main function and remaining pieces.

tools/cr/main.py

Index: tools/cr/main.py
diff --git a/tools/cr/main.py b/tools/cr/main.py
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+++ b/tools/cr/main.py
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+# Copyright (c) 2013 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.
+
+"""Chromium cr tool main module.
+
+Holds the main function and all it's support code.
+"""
+
+import os
+import sys
+import cr
+import cr.auto.user
+import cr.autocomplete
+import cr.loader
+
+_CONTACT = 'iancottrell@chromium.org'
+
+
+def Main():
+  """Chromium cr tool main function.
+
+  This is the main entry point of the cr tool, it finds and loads all the
+  plugins, creates the context and then activates and runs the specified
+  command.
+  """
+
+  # Add the users plugin dir to the cr.auto.user package scan
+  user_path = os.path.expanduser(os.path.join('~', '.config', 'cr'))
+  cr.auto.user.__path__.append(user_path)
+
+  cr.loader.Scan()
+
+  # Build the command context
+  context = cr.Context(
+      description='The chrome dev build tool.',
+      epilog='Contact ' + _CONTACT + ' if you have issues with this tool.',
+  )
+  # Install the sub-commands
+  for command in cr.Command.Plugins():
+    context.AddSubParser(command)
+
+  # test for the special autocomplete command
+  if context.autocompleting:
+    # After plugins are loaded so pylint: disable=g-import-not-at-top
+    cr.autocomplete.Complete(context)
+    return
+  # Speculative argument processing to add config specific args
+  context.ParseArgs(True)
+  cr.plugin.Activate(context)
+  # At this point we should know what command we are going to use
+  command = cr.Command.GetActivePlugin(context)
+  # Do some early processing, in case it changes the build dir
+  if command:
+    command.EarlyArgProcessing(context)
+  # Update the activated set again, in case the early processing changed it
+  cr.plugin.Activate(context)
+  # Load the build specific configuration
+  found_build_dir = cr.base.client.LoadConfig(context)
+  # Final processing or arguments
+  context.ParseArgs()
+  cr.plugin.Activate(context)
+  # If we did not get a command before, it might have been fixed.
+  if command is None:
+    command = cr.Command.GetActivePlugin(context)
+  # If the verbosity level is 3 or greater, then print the environment here
+  if context.verbose >= 3:
+    context.DumpValues(context.verbose > 3)
+  if command is None:
+    print context.Substitute('No command specified.')
+    exit(1)
+  if command.requires_build_dir:
+    if not found_build_dir:
+      if not context.Find('CR_OUT_FULL'):
+        print context.Substitute(
+            'No build directory specified. Please use cr init to make one.')
+      else:
+        print context.Substitute(
+            'Build {CR_BUILD_DIR} not a valid build directory')
+      exit(1)
+    if context.Find('CR_VERSION') != cr.base.client.VERSION:
+      print context.Substitute(
+          'Build {CR_BUILD_DIR} is for the wrong version of cr')
+      print 'Please run cr init to reset it'
+      exit(1)
+    cr.Platform.Prepare(context)
+  if context.verbose >= 1:
+    print context.Substitute(
+        'Running cr ' + command.name + ' for {CR_BUILD_DIR}')
+  # Invoke the given command
+  command.Run(context)
+
+if __name__ == '__main__':
+  sys.exit(Main())