convert: export revmap to source.

Sources may be able to use it to optimise their own log fetching

hgext/convert/__init__.py

@@ -216,6 +216,7 b' class convert(object):'
 
     def convert(self):
         try:
+            self.source.setrevmap(self.map)
             self.ui.status("scanning source...\n")
             heads = self.source.getheads()
             parents = self.walktree(heads)

hgext/convert/common.py

@@ -22,6 +22,11 b' class converter_source(object):'
         self.rev = rev
 
         self.encoding = 'utf-8'
+        self.revmap = {}
+
+    def setrevmap(self, revmap):
+        """set the map of already-converted revisions"""
+        self.revmap = revmap
 
     def getheads(self):
         """Return a list of this repository's heads"""