Add hook for deciding whether to tag a message.

It is useful for Context subclasses to be able to decide whether to tag
a message based on its content. For example, do not tag CTCP messages in
IRC.

Author: mmb

src/potr/context.py

@@ -282,7 +282,9 @@ def processOutgoingMessage(self, msg, flags, tlvs=[]):
                     # TODO notify
                     msg = self.user.getDefaultQueryMessage(self.getPolicy)
                 return msg
-            if self.getPolicy('SEND_TAG') and self.tagOffer != OFFER_REJECTED:
+            if self.getPolicy('SEND_TAG') and \
+                self.tagOffer != OFFER_REJECTED and \
+                self.shouldTagMessage(msg):
                 self.tagOffer = OFFER_SENT
                 versions = set()
                 if self.getPolicy('ALLOW_V1'):
@@ -492,6 +494,10 @@ def getExtraKey(self, extraKeyAppId=None, extraKeyAppData=None, appdata=None):
             self.sendInternal(b'', tlvs=tlvs, appdata=appdata)
         return self.crypto.extraKey
 
+    def shouldTagMessage(self, msg):
+        """Hook to decide whether to tag a message based on its contents."""
+        return True
+
 class Account(object):
     contextclass = Context
     def __init__(self, name, protocol, maxMessageSize, privkey=None):