revset: use `subset &` in `filelog`

This takes advantage of the `fullreposet` smartness.

revset  #0: file(COPYING)
0) wall 3.179066 comb 3.180000 user 3.140000 sys 0.040000 (best of 3)
1) wall 2.723699 comb 2.730000 user 2.690000 sys 0.040000 (best of 4)

mercurial/revset.py

@@ -811,7 +811,7 b' def filelog(repo, subset, x):'
                 for fr in fl:
                     s.add(fl.linkrev(fr))
 
-    return subset.filter(s.__contains__)
+    return subset & s
 
 def first(repo, subset, x):
     """``first(set, [n])``