remote-curl: die directly with http error messages

When we encounter an unknown http error (e.g., a 403), we
hand the error code to http_error, which then prints it with
error(). After that we die with the redundant message "HTTP
request failed".

Instead, let's just drop http_error entirely, which does
nothing but pass arguments to error(), and instead die
directly with a useful message.

So before:

  $ git clone https://example.com/repo.git
  Cloning into 'repo'...
  error: unable to access 'https://example.com/repo.git': The requested URL returned error: 403 Forbidden
  fatal: HTTP request failed

and after:

  $ git clone https://example.com/repo.git
  Cloning into 'repo'...
  fatal: unable to access 'https://example.com/repo.git': The requested URL returned error: 403 Forbidden

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

remote-curl.c

@@ -216,8 +216,7 @@ static struct discovery* discover_refs(const char *service, int for_push)
 		die("Authentication failed for '%s'", url);
 	default:
 		show_http_message(&type, &buffer);
-		http_error(url);
-		die("HTTP request failed");
+		die("unable to access '%s': %s", url, curl_errorstr);
 	}
 
 	last= xcalloc(1, sizeof(*last_discovery));