bookmarks: add invalidate() to bookmark_repo

Cached bookmark information would not be reset when repo.invalidate()
was called, meaning (for instanced) guis would be left with out-of-date
bookmark info.  This patch fixes that by overriding bookmark_repo.invalidate()

hgext/bookmarks.py

@@ -296,6 +296,13 b' def reposetup(ui, repo):'
             tags.update(self._bookmarks)
             return (tags, tagtypes)
 
+        if hasattr(repo, 'invalidate'):
+            def invalidate(self):
+                super(bookmark_repo, self).invalidate()
+                for attr in ('_bookmarks', '_bookmarkcurrent'):
+                    if attr in self.__dict__:
+                        delattr(repo, attr)
+
     repo.__class__ = bookmark_repo
 
 def uisetup(ui):