Add "--incremental" option to "backup create" command in volume v2

Cinder V2 API supports creating volume backup with "--incremental"
option. However, OSC doesn't support this argument. So this patch adds
the "--incremental" option to allow users to create incremental style
backups.

Change-Id: Iefac5f1a6c9ef006ad9c22d4250ae6df50504781
Closes-Bug: 1600196

doc/source/command-objects/backup.rst

@@ -18,6 +18,7 @@ Create new backup
         [--description <description>]
         [--snapshot <snapshot>]
         [--force]
+        [--incremental]
         <volume>
 
 .. option:: --container <container>
@@ -44,6 +45,12 @@ Create new backup
 
     *Volume version 2 only*
 
+.. option:: --incremental
+
+    Perform an incremental backup
+
+    *Volume version 2 only*
+
 .. _backup_create-backup:
 .. describe:: <volume>
 

openstackclient/tests/volume/v2/test_backup.py

@@ -79,6 +79,7 @@ class TestBackupCreate(TestBackup):
             "--description", self.new_backup.description,
             "--container", self.new_backup.container,
             "--force",
+            "--incremental",
             "--snapshot", self.new_backup.snapshot_id,
             self.new_backup.volume_id,
         ]
@@ -87,6 +88,7 @@ class TestBackupCreate(TestBackup):
             ("description", self.new_backup.description),
             ("container", self.new_backup.container),
             ("force", True),
+            ("incremental", True),
             ("snapshot", self.new_backup.snapshot_id),
             ("volume", self.new_backup.volume_id),
         ]
@@ -100,6 +102,7 @@ class TestBackupCreate(TestBackup):
             name=self.new_backup.name,
             description=self.new_backup.description,
             force=True,
+            incremental=True,
             snapshot_id=self.new_backup.snapshot_id,
         )
         self.assertEqual(self.columns, columns)
@@ -126,6 +129,7 @@ class TestBackupCreate(TestBackup):
             name=None,
             description=self.new_backup.description,
             force=False,
+            incremental=False,
             snapshot_id=None,
         )
         self.assertEqual(self.columns, columns)

openstackclient/volume/v2/backup.py

@@ -59,6 +59,12 @@ class CreateBackup(command.ShowOne):
             default=False,
             help=_("Allow to back up an in-use volume")
         )
+        parser.add_argument(
+            '--incremental',
+            action='store_true',
+            default=False,
+            help=_("Perform an incremental backup")
+        )
         return parser
 
     def take_action(self, parsed_args):
@@ -75,6 +81,7 @@ class CreateBackup(command.ShowOne):
             name=parsed_args.name,
             description=parsed_args.description,
             force=parsed_args.force,
+            incremental=parsed_args.incremental,
             snapshot_id=snapshot_id,
         )
         backup._info.pop("links", None)

releasenotes/notes/bug-1600196-6a733dd4e3371df7.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    Add ``--incremental`` option to ``backup create`` command to allow users to
+    create incremental backups.
+    [Bug `1600196 <https://bugs.launchpad.net/python-openstackclient/+bug/1600196>`_]