graft: use revset for intersecting with ancestor set
This addresses a TODO added in
a1381eea7c7d (graft: do not use
`.remove` on a smart set (regression), 2014-04-28).
Differential Revision: https://phab.mercurial-scm.org/D7806
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown