[cr] Add 'cr args' command

This patch adds an 'args' command to cr which opens the configuration
for the currently selected out directory in a text editor (similarly to
'gn args').

Review URL: https://codereview.chromium.org/1220523004

Cr-Commit-Position: refs/heads/master@{#338274}

2 files changed, 38 insertions, 1 deletions

diff --git a/tools/cr/cr/base/client.py b/tools/cr/cr/base/client.py
index cb21222..4c89c46 100644
--- a/tools/cr/cr/base/client.py
+++ b/tools/cr/cr/base/client.py
@@ -218,7 +218,12 @@ def LoadConfig():
   build_config_dir = _MigrateAndGetConfigDir(use_build_dir=True)
   cr.auto.build.__path__.append(build_config_dir)
   cr.loader.Scan()
-  return hasattr(cr.auto.build, 'config')
+
+  if not hasattr(cr.auto.build, 'config'):
+    return False
+
+  cr.context.derived.Set(CR_BUILD_CONFIG_PATH=_GetConfigFile(build_config_dir))
+  return True
 
 
 def WriteConfig(use_build_dir, data):
diff --git a/tools/cr/cr/commands/args.py b/tools/cr/cr/commands/args.py
new file mode 100644
index 0000000..6427642
--- /dev/null
+++ b/tools/cr/cr/commands/args.py
@@ -0,0 +1,32 @@
+# Copyright 2015 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.
+
+"""A module for the args command."""
+
+import os
+
+import cr
+
+class ArgsCommand(cr.Command):
+  """The implementation of the args command.
+
+  The args command is meant for editing the current build configuration
+  in a text editor.
+  """
+
+  def __init__(self):
+    super(ArgsCommand, self).__init__()
+    self.help = 'Edit build configuration in a text editor'
+    self.description = ("""
+        Opens the configuration for the currently selected out directory in
+        a text editor.
+        """)
+
+  def Run(self):
+    build_config_path = cr.context.Get('CR_BUILD_CONFIG_PATH')
+    editor = os.environ.get('EDITOR', 'vi')
+    print 'Opening %s in a text editor (%s)...' % (build_config_path, editor)
+    cr.Host.Execute(editor, build_config_path)
+    # TODO(petrcermak): Figure out a way to do this automatically.
+    print 'Please run \'cr prepare\' if you modified the file'