.arcconfig

tests: additional test coverage of archive web command

This command is special in a few ways. First, it is the only command
using the write() function from WSGI's start_response() function.
Second, it is setting a custom content-disposition header.

We change the test so it prints out full details of the HTTP
response. We also save the response body to a file so we can
verify its size and hash. The hash check will help ensure that
archive generation is deterministic.

Differential Revision: https://phab.mercurial-scm.org/D2790

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}