remote-curl: let servers override http 404 advice

remote-curl: let servers override http 404 advice

When we get an http 404 trying to get the initial list of
refs from the server, we try to be helpful and remind the
user that update-server-info may need to be run. This looks
like:

  $ git clone https://github.com/non/existent
  Cloning into 'existent'...
  fatal: https://github.com/non/existent/info/refs?service=git-upload-pack not found: did you run git update-server-info on the server?

Suggesting update-server-info may be a good suggestion for
users who are in control of the server repo and who are
planning to set up dumb http. But for users of smart http,
and especially users who are not in control of the server
repo, the advice is useless and confusing.

The previous patch taught remote-curl to show custom advice
from the server when it is available. When we have shown
messages from the server, we can also drop our custom
advice; what the server has to say is likely to be more
accurate and helpful.

We not only drop the mention of update-server-info, but also
show only the main repo URL, not the full "info/refs" and
service parameter. These elements may be useful for
debugging a broken server configuration, but again, anything
the server has provided is likely to be more useful (and one
can still use GIT_CURL_VERBOSE to get much more complete
debugging information).

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