kas: Support --force-checkout argument

When checking out a repository the default behaviour is to abort if
local changes are present. If the new `--force-checkout` argument is
passed on the command line then any local changes will instead be
discarded so that the desired refspec can be checked out.

Signed-off-by: Paul Barker <pbarker@konsulko.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/kas.py

@@ -106,6 +106,9 @@ def setup_parser_common_args(parser):
     parser.add_argument('--skip',
                         help='Skip build steps',
                         default=[])
+    parser.add_argument('--force-checkout', action='store_true',
+                        help='Always checkout the desired refspec of each '
+                        'repository, discarding any local changes')
 
 def kas_get_argparser():
     """