Summary:
we now serialize the overlay data for each directory independently.
When we mount, we try to load the root overlay data. The children are lazy
loaded as the inodes are instantiated.
Structural changes cause the overlay data for the impacted dirs to get saved out.
I need to make a pass over this to fixup comments and so on, I just wanted to get this diff out first.
I moved the overlay stuff from `eden/fs/overlay` -> `eden/fs/inodes` since most
of the overlay-ness is handled in `TreeInode` now; the `Overlay` class is
really just for carrying around the paths and providing the serialization
helpers.
Reviewed By: simpkins
Differential Revision: D3787108
fbshipit-source-id: f0e089a829defd953535b9d0a96b102ac729261b