Merge branch 'ds/bundle-uri-4'

Merge branch 'ds/bundle-uri-4'

Bundle URIs part 4.

* ds/bundle-uri-4:
  clone: unbundle the advertised bundles
  bundle-uri: download bundles from an advertised list
  bundle-uri: allow relative URLs in bundle lists
  strbuf: introduce strbuf_strip_file_from_path()
  bundle-uri: serve bundle.* keys from config
  bundle-uri client: add helper for testing server
  transport: rename got_remote_heads
  bundle-uri client: add boolean transfer.bundleURI setting
  clone: request the 'bundle-uri' command when available
  t: create test harness for 'bundle-uri' command
  protocol v2: add server-side "bundle-uri" skeleton