adds dry run CLI option to test the program without changing data

module/common/cli_parser.py

@@ -50,6 +50,10 @@ def parse_command_line(version=None, self_description=None, version_date=None, d
     parser.add_argument("-l", "--log_level", choices=valid_log_levels, dest="log_level",
                         help="set log level (overrides config)")
 
+    parser.add_argument("-n", "--dry_run", action="store_true",
+                        help="Operate as usual but don't change anything in NetBox. Great if you want to test "
+                             "and see what would be changed.")
+
     parser.add_argument("-p", "--purge", action="store_true",
                         help="Remove (almost) all synced objects which were create by this script. "
                              "This is helpful if you want to start fresh or stop using this script.")

netbox-sync.py

@@ -105,6 +105,10 @@ def main():
 
     # if purge was selected we go ahead and remove all items which were managed by this tools
     if args.purge is True:
+
+        if args.dry_run is True:
+            do_error_exit("Purge not available with option 'dry_run'")
+
         nb_handler.just_delete_all_the_things()
 
         # that's it, we are done here
@@ -142,6 +146,11 @@ def main():
     # update all IP addresses
     inventory.query_ptr_records_for_all_ips()
 
+    if args.dry_run is True:
+        log.info("This is a dry run and we stop here. Running time: %s" %
+                 get_relative_time(datetime.now() - start_time))
+        exit(0)
+
     # update data in NetBox
     nb_handler.update_instance()