volume: Add missing 'volume list --offset' parameter

Looking at the code for the ancient v1 cinder API, we see that this
supported offset-style pagination [1][2][3]. Add this parameter,
simplifying a future patch to standardize pagination across OSC.

[1] https://github.com/openstack/cinder/blob/juno-eol/cinder/api/v1/volumes.py#L259
[2] https://github.com/openstack/cinder/blob/juno-eol/cinder/api/v1/volumes.py#L292
[3] https://github.com/openstack/cinder/blob/juno-eol/cinder/api/common.py#L120

Change-Id: Ifec208ea9ed7afb4bebced6132abb96a3af034b5
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

openstackclient/tests/unit/volume/v1/test_volume.py

@@ -858,9 +858,10 @@ class TestVolumeList(TestVolume):
         ), )
         self.assertItemsEqual(datalist, tuple(data))
 
-    def test_volume_list_with_limit(self):
+    def test_volume_list_with_limit_and_offset(self):
         arglist = [
             '--limit', '2',
+            '--offset', '5',
         ]
         verifylist = [
             ('long', False),
@@ -868,6 +869,7 @@ class TestVolumeList(TestVolume):
             ('name', None),
             ('status', None),
             ('limit', 2),
+            ('offset', 5),
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
@@ -876,9 +878,11 @@ class TestVolumeList(TestVolume):
         self.volumes_mock.list.assert_called_once_with(
             limit=2,
             search_opts={
+                'offset': 5,
                 'status': None,
                 'display_name': None,
-                'all_tenants': False, }
+                'all_tenants': False,
+            },
         )
         self.assertEqual(self.columns, columns)
         self.assertItemsEqual(self.datalist, tuple(data))

openstackclient/volume/v1/volume.py

@@ -327,6 +327,13 @@ class ListVolume(command.Lister):
             default=False,
             help=_('List additional fields in output'),
         )
+        parser.add_argument(
+            '--offset',
+            type=int,
+            action=parseractions.NonNegativeAction,
+            metavar='<offset>',
+            help=_('Index from which to start listing volumes'),
+        )
         parser.add_argument(
             '--limit',
             type=int,
@@ -395,6 +402,9 @@ class ListVolume(command.Lister):
             'status': parsed_args.status,
         }
 
+        if parsed_args.offset:
+            search_opts['offset'] = parsed_args.offset
+
         data = volume_client.volumes.list(
             search_opts=search_opts,
             limit=parsed_args.limit,