revset-parentspec: call 'getset' on a 'fullreposet'
Calling 'baseset(repo.changelog)' builds a list for all revisions in
the repo. And we already have the lazy and efficient 'fullreposet'
class for this purpose.
This gives us the usual benefits of the fullreposet:
revset) 100^1
before) wall 0.002694 comb 0.000000 user 0.000000 sys 0.000000 (best of 897)
after) wall 0.000997 comb 0.000000 user 0.000000 sys 0.000000 (best of 2324)
revset) parents(100)^1
before) wall 0.003832 comb 0.000000 user 0.000000 sys 0.000000 (best of 587)
after) wall 0.001034 comb 0.000000 user 0.000000 sys 0.000000 (best of 2309)
revset) (100^1)^1
before) wall 0.005616 comb 0.000000 user 0.000000 sys 0.000000 (best of 405)
after) wall 0.001030 comb 0.000000 user 0.000000 sys 0.000000 (best of 2258)