--- a/mercurial/context.py	Sat Jul 12 17:57:25 2014 -0700
+++ b/mercurial/context.py	Sat Jul 12 17:59:03 2014 -0700
@@ -71,9 +71,13 @@
         object oriented way for other contexts to customize the manifest
         generation.
         """
+        if match.always():
+            return self.manifest().copy()
+
+        if match.matchfn == match.exact:
+            return self.manifest().intersectfiles(match.files())
+
         mf = self.manifest().copy()
-        if match.always():
-            return mf
         for fn in mf.keys():
             if not match(fn):
                 del mf[fn]