t5551: handle HTTP/2 when checking curl trace

t5551: handle HTTP/2 when checking curl trace

We check that the curl trace of a clone has the lines we expect, but
this won't work when we run the test under t5559, because a few details
are different under HTTP/2 (but nobody noticed because it only happens
when you manually set GIT_TEST_PROTOCOL_VERSION to "0").

We can handle both HTTP protocols with a few tweaks:

  - we'll drop the HTTP "101 Switching Protocols" response, as well as
    various protocol upgrade headers. These details aren't interesting
    to us. We just want to make sure the correct protocol was used (and
    we do in the main request/response lines).

  - successful HTTP/2 responses just say "200" and not "200 OK"; we can
    normalize these

  - replace HTTP/1.1 with a variable in the request/response lines. We
    can use the existing $HTTP_PROTO for this, as it's already set to
    "HTTP/2" when appropriate. We do need to tweak the fallback value to
    "HTTP/1.1" to match what curl will write (prior to this patch, the
    fallback value didn't matter at all; we only checked if it was the
    literal string "HTTP/2").

Note that several lines still expect HTTP/1.1 unconditionally. The first
request does so because the client requests an upgrade during the
request. The POST request and response do so because you can't do an
upgrade if there is a request body. (This will all be different if we
trigger HTTP/2 via ALPN, but the tests aren't yet capable of that).

This is enough to let:

  GIT_TEST_PROTOCOL_VERSION=0 ./t5559-http-fetch-smart-http2.sh

pass the "clone http repository" test (but there are some other failures
later on).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>