Merge branch 'jk/dumb-http-alternate-fix'

The HTTP walker misinterpreted the alternates file that gives an
absolute path when the server URL does not have the final slash
(i.e., "https://example.com" not "https://example.com/").

* jk/dumb-http-alternate-fix:
  http: handle absolute-path alternates from server root

diff --cc http-walker.c
Simple merge

diff --cc t/t5550-http-fetch-dumb.sh
Simple merge