histedit: add tostate method to histedit action

the format of rules that we store in state file format is different from the rule
format that we present to users. We need a way of dumping action to state file.

hgext/histedit.py

@@ -376,6 +376,12 b' class histeditaction(object):'
         maxlen = max(maxlen, 22) # avoid truncating hash
         return util.ellipsis(line, maxlen)
 
+    def tostate(self):
+        """Print an action in format used by histedit state files
+           (the first line is a verb, the remainder is the second)
+        """
+        return "%s\n%s" % (self.verb, node.hex(self.node))
+
     def constraints(self):
         """Return a set of constrains that this action should be verified for
         """