http: avoid disconnecting on 404s for loose objects

404s are common when fetching loose objects on static HTTP
servers, and reestablishing a connection for every single
404 adds additional latency.

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-walker.c

@@ -488,6 +488,15 @@ static int fetch_object(struct walker *walker, unsigned char *sha1)
 		req->localfile = -1;
 	}
 
+	/*
+	 * we turned off CURLOPT_FAILONERROR to avoid losing a
+	 * persistent connection and got CURLE_OK.
+	 */
+	if (req->http_code == 404 && req->curl_result == CURLE_OK &&
+			(starts_with(req->url, "http://") ||
+			 starts_with(req->url, "https://")))
+		req->curl_result = CURLE_HTTP_RETURNED_ERROR;
+
 	if (obj_req->state == ABORTED) {
 		ret = error("Request for %s aborted", hex);
 	} else if (req->curl_result != CURLE_OK &&

http.c

@@ -1855,8 +1855,19 @@ static size_t fwrite_sha1_file(char *ptr, size_t eltsize, size_t nmemb,
 	unsigned char expn[4096];
 	size_t size = eltsize * nmemb;
 	int posn = 0;
-	struct http_object_request *freq =
-		(struct http_object_request *)data;
+	struct http_object_request *freq = data;
+	struct active_request_slot *slot = freq->slot;
+
+	if (slot) {
+		CURLcode c = curl_easy_getinfo(slot->curl, CURLINFO_HTTP_CODE,
+						&slot->http_code);
+		if (c != CURLE_OK)
+			die("BUG: curl_easy_getinfo for HTTP code failed: %s",
+				curl_easy_strerror(c));
+		if (slot->http_code >= 400)
+			return size;
+	}
+
 	do {
 		ssize_t retval = xwrite(freq->localfile,
 					(char *) ptr + posn, size - posn);
@@ -1977,6 +1988,7 @@ struct http_object_request *new_http_object_request(const char *base_url,
 	freq->slot = get_active_slot();
 
 	curl_easy_setopt(freq->slot->curl, CURLOPT_FILE, freq);
+	curl_easy_setopt(freq->slot->curl, CURLOPT_FAILONERROR, 0);
 	curl_easy_setopt(freq->slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
 	curl_easy_setopt(freq->slot->curl, CURLOPT_ERRORBUFFER, freq->errorstr);
 	curl_easy_setopt(freq->slot->curl, CURLOPT_URL, freq->url);