--- a/mercurial/cmdutil.py	Sun Sep 07 11:46:11 2014 -0500
+++ b/mercurial/cmdutil.py	Sat Aug 30 02:47:59 2014 +0200
@@ -2527,6 +2527,9 @@
             (unknown,    actions['unknown'],  discard),
             )
 
+        needdata = ('revert', 'add', 'remove', 'undelete')
+        _revertprefetch(repo, ctx, *[actions[name][0] for name in needdata])
+
         for abs, (rel, exact) in sorted(names.items()):
             # target file to be touch on disk (relative to cwd)
             target = repo.wjoin(abs)
@@ -2564,6 +2567,10 @@
     finally:
         wlock.release()
 
+def _revertprefetch(repo, ctx, *files):
+    """Let extension changing the storage layer prefetch content"""
+    pass
+
 def _performrevert(repo, parents, ctx, actions):
     """function that actually perform all the actions computed for revert