mergestate: add a method to compute actions to perform on dirstate

We're going to use this to extend the action lists in merge.applyupdates.

The somewhat funky return value is to make passing this dict directly into
recordactions easier. We're going to exploit that in an upcoming patch.

mercurial/merge.py

@@ -509,6 +509,14 b' class mergestate(object):'
         return len([True for f, entry in self._state.iteritems()
                     if entry[0] == 'u'])
 
+    def actions(self):
+        """return lists of actions to perform on the dirstate"""
+        actions = {'r': [], 'a': [], 'g': []}
+        for f, (r, action) in self._results.iteritems():
+            if action is not None:
+                actions[action].append((f, None, "merge result"))
+        return actions
+
 def _checkunknownfile(repo, wctx, mctx, f, f2=None):
     if f2 is None:
         f2 = f