Summary:
Prefetching metadata for the entries in a tree when we fetch it saves us
an extra round trip to the server to fetch a blob when only the metadata
for that blob is fetched. (This can happen often while parsing targets in
builds)
This implements a custom metadata fetcher to fetch this data when we
fetch a tree from the server.
Reviewed By: chadaustin
Differential Revision: D22086639
fbshipit-source-id: 5fe31d375bf6f7376eb67496d553d6b4540fc0c9
d2b4855372