http: refactor finish_http_pack_request()

finish_http_pack_request() does multiple tasks, including some
housekeeping on a struct packed_git - (1) closing its index, (2)
removing it from a list, and (3) installing it. These concerns are
independent of fetching a pack through HTTP: they are there only because
(1) the calling code opens the pack's index before deciding to fetch it,
(2) the calling code maintains a list of packfiles that can be fetched,
and (3) the calling code fetches it in order to make use of its objects
in the same process.

In preparation for a subsequent commit, which adds a feature that does
not need any of this housekeeping, remove (1), (2), and (3) from
finish_http_pack_request(). (2) and (3) are now done by a helper
function, and (1) is the responsibility of the caller (in this patch,
done closer to the point where the pack index is opened).

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -117,6 +117,7 @@ enum transfer_state {
 
 struct transfer_request {
 	struct object *obj;
+	struct packed_git *target;
 	char *url;
 	char *dest;
 	struct remote_lock *lock;
@@ -314,17 +315,18 @@ static void start_fetch_packed(struct transfer_request *request)
 		release_request(request);
 		return;
 	}
+	close_pack_index(target);
+	request->target = target;
 
 	fprintf(stderr,	"Fetching pack %s\n",
 		hash_to_hex(target->hash));
 	fprintf(stderr, " which contains %s\n", oid_to_hex(&request->obj->oid));
 
-	preq = new_http_pack_request(target, repo->url);
+	preq = new_http_pack_request(target->hash, repo->url);
 	if (preq == NULL) {
 		repo->can_update_info_refs = 0;
 		return;
 	}
-	preq->lst = &repo->packs;
 
 	/* Make sure there isn't another open request for this pack */
 	while (check_request) {
@@ -597,6 +599,8 @@ static void finish_request(struct transfer_request *request)
 		}
 		if (fail)
 			repo->can_update_info_refs = 0;
+		else
+			http_install_packfile(request->target, &repo->packs);
 		release_request(request);
 	}
 }

http-walker.c

@@ -439,6 +439,7 @@ static int http_fetch_pack(struct walker *walker, struct alt_base *repo, unsigne
 	target = find_sha1_pack(sha1, repo->packs);
 	if (!target)
 		return -1;
+	close_pack_index(target);
 
 	if (walker->get_verbosely) {
 		fprintf(stderr, "Getting pack %s\n",
@@ -447,10 +448,9 @@ static int http_fetch_pack(struct walker *walker, struct alt_base *repo, unsigne
 			hash_to_hex(sha1));
 	}
 
-	preq = new_http_pack_request(target, repo->base);
+	preq = new_http_pack_request(target->hash, repo->base);
 	if (preq == NULL)
 		goto abort;
-	preq->lst = &repo->packs;
 	preq->slot->results = &results;
 
 	if (start_active_slot(preq->slot)) {
@@ -469,6 +469,7 @@ static int http_fetch_pack(struct walker *walker, struct alt_base *repo, unsigne
 	release_http_pack_request(preq);
 	if (ret)
 		return ret;
+	http_install_packfile(target, &repo->packs);
 
 	return 0;
 

http.c

@@ -2268,22 +2268,13 @@ void release_http_pack_request(struct http_pack_request *preq)
 
 int finish_http_pack_request(struct http_pack_request *preq)
 {
-	struct packed_git **lst;
-	struct packed_git *p = preq->target;
 	struct child_process ip = CHILD_PROCESS_INIT;
 	int tmpfile_fd;
 	int ret = 0;
 
-	close_pack_index(p);
-
 	fclose(preq->packfile);
 	preq->packfile = NULL;
 
-	lst = preq->lst;
-	while (*lst != p)
-		lst = &((*lst)->next);
-	*lst = (*lst)->next;
-
 	tmpfile_fd = xopen(preq->tmpfile.buf, O_RDONLY);
 
 	argv_array_push(&ip.args, "index-pack");
@@ -2297,15 +2288,26 @@ int finish_http_pack_request(struct http_pack_request *preq)
 		goto cleanup;
 	}
 
-	install_packed_git(the_repository, p);
 cleanup:
 	close(tmpfile_fd);
 	unlink(preq->tmpfile.buf);
 	return ret;
 }
 
+void http_install_packfile(struct packed_git *p,
+			   struct packed_git **list_to_remove_from)
+{
+	struct packed_git **lst = list_to_remove_from;
+
+	while (*lst != p)
+		lst = &((*lst)->next);
+	*lst = (*lst)->next;
+
+	install_packed_git(the_repository, p);
+}
+
 struct http_pack_request *new_http_pack_request(
-	struct packed_git *target, const char *base_url)
+	const unsigned char *packed_git_hash, const char *base_url)
 {
 	off_t prev_posn = 0;
 	struct strbuf buf = STRBUF_INIT;
@@ -2313,14 +2315,13 @@ struct http_pack_request *new_http_pack_request(
 
 	preq = xcalloc(1, sizeof(*preq));
 	strbuf_init(&preq->tmpfile, 0);
-	preq->target = target;
 
 	end_url_with_slash(&buf, base_url);
 	strbuf_addf(&buf, "objects/pack/pack-%s.pack",
-		hash_to_hex(target->hash));
+		hash_to_hex(packed_git_hash));
 	preq->url = strbuf_detach(&buf, NULL);
 
-	strbuf_addf(&preq->tmpfile, "%s.temp", sha1_pack_name(target->hash));
+	strbuf_addf(&preq->tmpfile, "%s.temp", sha1_pack_name(packed_git_hash));
 	preq->packfile = fopen(preq->tmpfile.buf, "a");
 	if (!preq->packfile) {
 		error("Unable to open local file %s for pack",
@@ -2344,7 +2345,7 @@ struct http_pack_request *new_http_pack_request(
 		if (http_is_verbose)
 			fprintf(stderr,
 				"Resuming fetch of pack %s at byte %"PRIuMAX"\n",
-				hash_to_hex(target->hash),
+				hash_to_hex(packed_git_hash),
 				(uintmax_t)prev_posn);
 		http_opt_request_remainder(preq->slot->curl, prev_posn);
 	}

http.h

@@ -216,18 +216,25 @@ int http_get_info_packs(const char *base_url,
 
 struct http_pack_request {
 	char *url;
-	struct packed_git *target;
-	struct packed_git **lst;
 	FILE *packfile;
 	struct strbuf tmpfile;
 	struct active_request_slot *slot;
 };
 
 struct http_pack_request *new_http_pack_request(
-	struct packed_git *target, const char *base_url);
+	const unsigned char *packed_git_hash, const char *base_url);
 int finish_http_pack_request(struct http_pack_request *preq);
 void release_http_pack_request(struct http_pack_request *preq);
 
+/*
+ * Remove p from the given list, and invoke install_packed_git() on it.
+ *
+ * This is a convenience function for users that have obtained a list of packs
+ * from http_get_info_packs() and have chosen a specific pack to fetch.
+ */
+void http_install_packfile(struct packed_git *p,
+			   struct packed_git **list_to_remove_from);
+
 /* Helpers for fetching object */
 struct http_object_request {
 	char *url;