reachableroots: unroll loop that checks if one of parents is reachable
The difference is small, but fewer loops should be better in general:
revset #0: 0::tip
0) 0.001609
1) 0.001510 93%
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 4 changes to 4 files
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 4 changes to 4 files
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved