Restore functionality to allow proxies to cache objects

The parallel request changes didn't properly implement the previous patch to
allow caching of retrieved objects by proxy servers.  Restore the previous
functionality such that by default requests include the "Pragma: no-cache"
header, and this header is removed on requests for pack indexes, packs, and
objects.

Signed-off-by: Nick Hengeveld <nickh@reactrix.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

http-fetch.c

@@ -29,6 +29,7 @@ static int max_requests = DEFAULT_MAX_REQUESTS;
 static CURLM *curlm;
 #endif
 static CURL *curl_default;
+static struct curl_slist *pragma_header;
 static struct curl_slist *no_pragma_header;
 static struct curl_slist *no_range_header;
 static char curl_errorstr[CURL_ERROR_SIZE];
@@ -203,7 +204,7 @@ struct active_request_slot *get_active_slot()
 	slot->in_use = 1;
 	slot->done = 0;
 	slot->local = NULL;
-	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, pragma_header);
 	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_range_header);
 	curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, curl_errorstr);
 
@@ -358,6 +359,7 @@ void start_request(struct transfer_request *request)
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
 	curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, request->errorstr);
 	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
 
 	/* If we have successfully processed data from a previous fetch
 	   attempt, only fetch the data we don't already have. */
@@ -568,6 +570,7 @@ static int fetch_index(struct alt_base *repo, unsigned char *sha1)
 	curl_easy_setopt(slot->curl, CURLOPT_FILE, indexfile);
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
 	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
 	slot->local = indexfile;
 
 	/* If there is data present from a previous transfer attempt,
@@ -837,6 +840,7 @@ static int fetch_pack(struct alt_base *repo, unsigned char *sha1)
 	curl_easy_setopt(slot->curl, CURLOPT_FILE, packfile);
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
 	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
 	slot->local = packfile;
 
 	/* If there is data present from a previous transfer attempt,
@@ -1067,6 +1071,7 @@ int main(int argc, char **argv)
 		return 1;
 	}
 #endif
+	pragma_header = curl_slist_append(pragma_header, "Pragma: no-cache");
 	no_pragma_header = curl_slist_append(no_pragma_header, "Pragma:");
 	no_range_header = curl_slist_append(no_range_header, "Range:");
 
@@ -1106,6 +1111,7 @@ int main(int argc, char **argv)
 	if (pull(commit_id))
 		return 1;
 
+	curl_slist_free_all(pragma_header);
 	curl_slist_free_all(no_pragma_header);
 	curl_slist_free_all(no_range_header);
 	curl_easy_cleanup(curl_default);