fetch-pack: unify ref in and out param

When a user fetches:
 - at least one up-to-date ref and at least one non-up-to-date ref,
 - using HTTP with protocol v0 (or something else that uses the fetch
   command of a remote helper)
some refs might not be updated after the fetch.

This bug was introduced in commit 989b8c4452 ("fetch-pack: put shallow
info in output parameter", 2018-06-28) which allowed transports to
report the refs that they have fetched in a new out-parameter
"fetched_refs". If they do so, transport_fetch_refs() makes this
information available to its caller.

Users of "fetched_refs" rely on the following 3 properties:
 (1) it is the complete list of refs that was passed to
     transport_fetch_refs(),
 (2) it has shallow information (REF_STATUS_REJECT_SHALLOW set if
     relevant), and
 (3) it has updated OIDs if ref-in-want was used (introduced after
     989b8c4452).

In an effort to satisfy (1), whenever transport_fetch_refs()
filters the refs sent to the transport, it re-adds the filtered refs to
whatever the transport supplies before returning it to the user.
However, the implementation in 989b8c4452 unconditionally re-adds the
filtered refs without checking if the transport refrained from reporting
anything in "fetched_refs" (which it is allowed to do), resulting in an
incomplete list, no longer satisfying (1).

An earlier effort to resolve this [1] solved the issue by readding the
filtered refs only if the transport did not refrain from reporting in
"fetched_refs", but after further discussion, it seems that the better
solution is to revert the API change that introduced "fetched_refs".
This API change was first suggested as part of a ref-in-want
implementation that allowed for ref patterns and, thus, there could be
drastic differences between the input refs and the refs actually fetched
[2]; we eventually decided to only allow exact ref names, but this API
change remained even though its necessity was decreased.

Therefore, revert this API change by reverting commit 989b8c4452, and
make receive_wanted_refs() update the OIDs in the sought array (like how
update_shallow() updates shallow information in the sought array)
instead. A test is also included to show that the user-visible bug
discussed at the beginning of this commit message no longer exists.

[1] https://public-inbox.org/git/20180801171806.GA122458@google.com/
[2] https://public-inbox.org/git/86a128c5fb710a41791e7183207c4d64889f9307.1485381677.git.jonathantanmy@google.com/

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

1 files changed, 15 insertions, 15 deletions

diff --git a/fetch-pack.c b/fetch-pack.c
index 60bbffb..660259e 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1338,25 +1338,26 @@ static void receive_shallow_info(struct fetch_pack_args *args,
 	args->deepen = 1;
 }
 
-static void receive_wanted_refs(struct packet_reader *reader, struct ref *refs)
+static void receive_wanted_refs(struct packet_reader *reader,
+				struct ref **sought, int nr_sought)
 {
 	process_section_header(reader, "wanted-refs", 0);
 	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
 		struct object_id oid;
 		const char *end;
-		struct ref *r = NULL;
+		int i;
 
 		if (parse_oid_hex(reader->line, &oid, &end) || *end++ != ' ')
 			die("expected wanted-ref, got '%s'", reader->line);
 
-		for (r = refs; r; r = r->next) {
-			if (!strcmp(end, r->name)) {
-				oidcpy(&r->old_oid, &oid);
+		for (i = 0; i < nr_sought; i++) {
+			if (!strcmp(end, sought[i]->name)) {
+				oidcpy(&sought[i]->old_oid, &oid);
 				break;
 			}
 		}
 
-		if (!r)
+		if (i == nr_sought)
 			die("unexpected wanted-ref: '%s'", reader->line);
 	}
 
@@ -1439,7 +1440,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				receive_shallow_info(args, &reader);
 
 			if (process_section_header(&reader, "wanted-refs", 1))
-				receive_wanted_refs(&reader, ref);
+				receive_wanted_refs(&reader, sought, nr_sought);
 
 			/* get the pack */
 			process_section_header(&reader, "packfile", 0);
@@ -1503,13 +1504,12 @@ static int remove_duplicates_in_refs(struct ref **ref, int nr)
 }
 
 static void update_shallow(struct fetch_pack_args *args,
-			   struct ref *refs,
+			   struct ref **sought, int nr_sought,
 			   struct shallow_info *si)
 {
 	struct oid_array ref = OID_ARRAY_INIT;
 	int *status;
 	int i;
-	struct ref *r;
 
 	if (args->deepen && alternate_shallow_file) {
 		if (*alternate_shallow_file == '\0') { /* --unshallow */
@@ -1551,8 +1551,8 @@ static void update_shallow(struct fetch_pack_args *args,
 	remove_nonexistent_theirs_shallow(si);
 	if (!si->nr_ours && !si->nr_theirs)
 		return;
-	for (r = refs; r; r = r->next)
-		oid_array_append(&ref, &r->old_oid);
+	for (i = 0; i < nr_sought; i++)
+		oid_array_append(&ref, &sought[i]->old_oid);
 	si->ref = &ref;
 
 	if (args->update_shallow) {
@@ -1586,12 +1586,12 @@ static void update_shallow(struct fetch_pack_args *args,
 	 * remote is also shallow, check what ref is safe to update
 	 * without updating .git/shallow
 	 */
-	status = xcalloc(ref.nr, sizeof(*status));
+	status = xcalloc(nr_sought, sizeof(*status));
 	assign_shallow_commits_to_refs(si, NULL, status);
 	if (si->nr_ours || si->nr_theirs) {
-		for (r = refs, i = 0; r; r = r->next, i++)
+		for (i = 0; i < nr_sought; i++)
 			if (status[i])
-				r->status = REF_STATUS_REJECT_SHALLOW;
+				sought[i]->status = REF_STATUS_REJECT_SHALLOW;
 	}
 	free(status);
 	oid_array_clear(&ref);
@@ -1654,7 +1654,7 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		args->connectivity_checked = 1;
 	}
 
-	update_shallow(args, ref_cpy, &si);
+	update_shallow(args, sought, nr_sought, &si);
 cleanup:
 	clear_shallow_info(&si);
 	return ref_cpy;