Merge branch 'jt/cdn-offload'

The "fetch/clone" protocol has been updated to allow the server to instruct the clients to grab pre-packaged packfile(s) in addition to the packed object data coming over the wire. * jt/cdn-offload: upload-pack: fix a sparse '0 as NULL pointer' warning upload-pack: send part of packfile response as uri fetch-pack: support more than one pack lockfile upload-pack: refactor reading of pack-objects out Documentation: add Packfile URIs design doc Documentation: order protocol v2 sections http-fetch: support fetching packfiles by URL http-fetch: refactor into function http: refactor finish_http_pack_request() http: use --stdin when indexing dumb HTTP pack