convert: add before/after hooks for converter sources

hgext/convert/__init__.py

@@ -235,6 +235,7 b' class converter(object):'
 
     def convert(self):
         try:
+            self.source.before()
             self.dest.before()
             self.source.setrevmap(self.map)
             self.ui.status("scanning source...\n")
@@ -273,7 +274,10 b' class converter(object):'
             self.cleanup()
 
     def cleanup(self):
-        self.dest.after()
+        try:
+            self.dest.after()
+        finally:
+            self.source.after()
         if self.revmapfilefd:
             self.revmapfilefd.close()
 

hgext/convert/common.py

@@ -38,6 +38,12 b' class converter_source(object):'
 
         self.encoding = 'utf-8'
 
+    def before(self):
+        pass
+
+    def after(self):
+        pass
+
     def setrevmap(self, revmap):
         """set the map of already-converted revisions"""
         pass