Multiple API version support

* Use multiple entry point groups to represent each API+version
  combination supported
* Add some tests

Try it out:
* Right now only '* user' commands have multiple overlapping versions;
  you can see the selection between v2.0 and v3 by looking at the
  command help output for 'tenant' vs 'project':

  os --os-identity-api-version=2.0 help set user
  os --os-identity-api-version=3 help set user

Change-Id: I7114fd246843df0243d354a7cce697810bb7de62

1 files changed, 42 insertions, 0 deletions

diff --git a/openstackclient/common/commandmanager.py b/openstackclient/common/commandmanager.py
new file mode 100644
index 00000000..e366034a
--- /dev/null
+++ b/openstackclient/common/commandmanager.py
@@ -0,0 +1,42 @@
+#   Copyright 2012-2013 OpenStack, LLC.
+#
+#   Licensed under the Apache License, Version 2.0 (the "License"); you may
+#   not use this file except in compliance with the License. You may obtain
+#   a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#   WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#   License for the specific language governing permissions and limitations
+#   under the License.
+#
+
+"""Modify Cliff's CommandManager"""
+
+import logging
+import pkg_resources
+
+import cliff.commandmanager
+
+
+LOG = logging.getLogger(__name__)
+
+
+class CommandManager(cliff.commandmanager.CommandManager):
+    """Alters Cliff's default CommandManager behaviour to load additiona
+       command groups after initialization.
+    """
+    def _load_commands(self, group=None):
+        if not group:
+            group = self.namespace
+        for ep in pkg_resources.iter_entry_points(group):
+            LOG.debug('found command %r' % ep.name)
+            self.commands[ep.name.replace('_', ' ')] = ep
+        return
+
+    def add_command_group(self, group=None):
+        """Adds another group of command entrypoints"""
+        if group:
+            self._load_commands(group)