graphmod: restore generator nature of dagwalker...
graphmod: restore generator nature of dagwalker
9966c95b8c4f introduced the ability to walk the DAG
given arbitrary revisions, but changed the behaviour of
it to return a list of all nodes (and create a changectx
for each one) rather than doing it lazily.
This has a pretty significant impact on performance for large
repositories (tested on CPython repo, with output disabled):
$ time hg glog
real 0m2.642s
user 0m2.560s
sys 0m0.080s
Before 9966c95b8c4f:
$ time hg glog
real 0m0.143s
user 0m0.112s
sys 0m0.032s
And after this fix:
$ time hg glog
real 0m0.213s
user 0m0.184s
sys 0m0.028s
