diff --git a/mercurial/registrar.py b/mercurial/registrar.py
--- a/mercurial/registrar.py
+++ b/mercurial/registrar.py
@@ -145,6 +145,14 @@
             self._table[name] = func, list(options)
         return func
 
+class cmdtype(object):
+    """ enum for the type of command which will tell whether the command is
+    write, if so either recoverable or unrecoverable or just read only
+    """
+    UNRECOVERABLE_WRITE = "unrecoverable"
+    RECOVERABLE_WRITE = "recoverable"
+    READ_ONLY = "readonly"
+
 class revsetpredicate(_funcregistrarbase):
     """Decorator to register revset predicate