Add DELETE_CONFIRM_THRESHOLD option

dsc/const.py

@@ -3,3 +3,10 @@ DEFAULT_LIBS_DIR = "/dsc/seafile"
 DEPRECATED_LIBS_DIR = "/data"
 DEFAULT_USERNAME = "seafile"
 STATUS_POLL_PERIOD = 1
+
+AVAILABLE_SEAFCLI_OPTIONS = {
+    "delete_confirm_threshold",
+    "disable_verify_certificate",
+    "upload_limit",
+    "download_limit",
+}