Add support for parameters to translate template

Some templates can have substitutions for values used throughout
the template. We should expose this feature via the command
line.

partially implements bp openstack-client-heat-translator

Change-Id: Iee4c21285afa77e7e5b36437928b3d62c10e465e

translator/osc/utils.py

@@ -13,6 +13,7 @@
 
 """Common client utilities"""
 
+import argparse
 import os
 
 
@@ -27,3 +28,18 @@ def env(*vars, **kwargs):
         if value:
             return value
     return kwargs.get('default', '')
+
+
+class KeyValueAction(argparse.Action):
+    """A custom action to parse arguments as key=value pairs. """
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        # Make sure we have an empty dict rather than None
+        if getattr(namespace, self.dest, None) is None:
+            setattr(namespace, self.dest, {})
+
+        # Add value if an assignment else remove it
+        if '=' in values:
+            getattr(namespace, self.dest, {}).update([values.split('=', 1)])
+        else:
+            getattr(namespace, self.dest, {}).pop(values, None)

translator/osc/v1/translate.py

@@ -19,6 +19,7 @@ import sys
 from cliff import command
 
 from translator.hot.tosca_translator import TOSCATranslator
+from translator.osc import utils
 from translator.toscalib.tosca_template import ToscaTemplate
 
 
@@ -45,6 +46,13 @@ class TranslateTemplate(command.Command):
             '--output-file',
             metavar='<output-file>',
             help='Path to place the translated content.')
+        parser.add_argument(
+            '--parameter',
+            metavar='<key=value>',
+            action=utils.KeyValueAction,
+            help='Set a property for this template '
+                 '(repeat option to set multiple properties)',
+        )
         return parser
 
     def take_action(self, parsed_args):
@@ -54,8 +62,11 @@ class TranslateTemplate(command.Command):
             sys.stdout.write('Could not find template file.')
             raise SystemExit
 
-        # TODO(stevemar): parsed_params doesn't default nicely
+        if parsed_args.parameter:
+            parsed_params = parsed_args.parameter
+        else:
             parsed_params = {}
+
         if parsed_args.template_type == "tosca":
             tosca = ToscaTemplate(parsed_args.template_file)
             translator = TOSCATranslator(tosca, parsed_params)