Summary:
Let's pull node during update if not found locally.
This is a part of selectivepull functionality.
See remotenames extensions for details about selectivepull.
Test Plan: arc unit
Reviewers: #sourcecontrol, durham
Reviewed By: durham
Subscribers: indragie, mjpieters, sergeyb
Differential Revision: https://phabricator.intern.facebook.com/D4536129
Tasks: 12479658
Signature: t1:4536129:1486667537:3d1df30cb5d1db0dd7451756102ccafee20789d5