Merge branch 'rc/http-push'

Merge branch 'rc/http-push'

* rc/http-push: (22 commits)
  http*: add helper methods for fetching objects (loose)
  http*: add helper methods for fetching packs
  http: use new http API in fetch_index()
  http*: add http_get_info_packs
  http-push.c::fetch_symref(): use the new http API
  http-push.c::remote_exists(): use the new http API
  http.c::http_fetch_ref(): use the new http API
  transport.c::get_refs_via_curl(): use the new http API
  http.c: new functions for the http API
  http: create function end_url_with_slash
  http*: move common variables and macros to http.[ch]
  transport.c::get_refs_via_curl(): do not leak refs_url
  Don't expect verify_pack() callers to set pack_size
  http-push: do not SEGV after fetching a bad pack idx file
  http*: copy string returned by sha1_to_hex
  http-walker: verify remote packs
  http-push, http-walker: style fixes
  t5550-http-fetch: test fetching of packed objects
  http-push: fix missing "#ifdef USE_CURL_MULTI" around "is_running_queue"
  http-push: send out fetch requests on queue
  ...