Extract base classes from cmdlib

Base classes holding common functionality is extracted into base.py.
Utility functions used by both base classes and subclasses is moved to
common.py.
Signed-off-by: Thomas Thrainer <thomasth@google.com>
Reviewed-by: Bernardo Dal Seno <bdalseno@google.com>

Makefile.am

@@ -308,7 +308,9 @@ client_PYTHON = \
 	lib/client/gnt_storage.py
 
 cmdlib_PYTHON = \
-	lib/cmdlib/__init__.py
+	lib/cmdlib/__init__.py \
+	lib/cmdlib/common.py \
+	lib/cmdlib/base.py
 
 hypervisor_PYTHON = \
 	lib/hypervisor/__init__.py \

lib/cmdlib/common.py

+#
+#
+
+# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Google Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA.
+
+
+"""Common functions used by multiple logical units."""
+
+from ganeti import errors
+
+
+def _ExpandItemName(fn, name, kind):
+  """Expand an item name.
+
+  @param fn: the function to use for expansion
+  @param name: requested item name
+  @param kind: text description ('Node' or 'Instance')
+  @return: the resolved (full) name
+  @raise errors.OpPrereqError: if the item is not found
+
+  """
+  full_name = fn(name)
+  if full_name is None:
+    raise errors.OpPrereqError("%s '%s' not known" % (kind, name),
+                               errors.ECODE_NOENT)
+  return full_name
+
+
+def _ExpandInstanceName(cfg, name):
+  """Wrapper over L{_ExpandItemName} for instance."""
+  return _ExpandItemName(cfg.ExpandInstanceName, name, "Instance")
+
+
+def _ExpandNodeName(cfg, name):
+  """Wrapper over L{_ExpandItemName} for nodes."""
+  return _ExpandItemName(cfg.ExpandNodeName, name, "Node")