Merge branch 'ds/bundle-uri'

Merge branch 'ds/bundle-uri'

Preliminary code refactoring around transport and bundle code.

* ds/bundle-uri:
  bundle.h: make "fd" version of read_bundle_header() public
  remote: allow relative_url() to return an absolute url
  remote: move relative_url()
  http: make http_get_file() external
  fetch-pack: move --keep=* option filling to a function
  fetch-pack: add a deref_without_lazy_fetch_extended()
  dir API: add a generalized path_match_flags() function
  connect.c: refactor sending of agent & object-format