rust: less set lookups in AncestorsIterator
This uses the boolean return of `HashSet::insert()` to factor
pairs of contains()/insert() into a single insert()
On the mozilla-central repository (450k changesets), I get about a bit more
than 10% better medians in perfancestors (taking the mean of three runs)
Best run for parent changeset:
! wall 0.106474 comb 0.110000 user 0.110000 sys 0.000000 (median of 93)
Best run for this changeset:
! wall 0.093191 comb 0.090000 user 0.090000 sys 0.000000 (median of 100)
Differential Revision: https://phab.mercurial-scm.org/D5942
#!/usr/bin/env python
from __future__ import absolute_import, print_function
import errno
import os
import sys
for f in sys.argv[1:]:
try:
print(f, '->', os.readlink(f))
except OSError as err:
if err.errno != errno.EINVAL:
raise
print(f, '->', f, 'not a symlink')
sys.exit(0)