context: add tags() method

mercurial/context.py

@@ -67,6 +67,7 b' class changectx(object):'
     def files(self): return self._changeset[3]
     def description(self): return self._changeset[4]
     def branch(self): return self._changeset[5].get("branch")
+    def tags(self): return self._repo.nodetags(self._node)
 
     def parents(self):
         """return contexts for each parent changeset"""
@@ -413,6 +414,11 b' class workingctx(changectx):'
     def clean(self): return self._status[5]
     def branch(self): return self._repo.dirstate.branch()
 
+    def tags(self):
+        t = []
+        [t.extend(p.tags()) for p in self.parents()]
+        return t
+
     def parents(self):
         """return contexts for each parent changeset"""
         return self._parents