midx: stop using linked list when closing MIDX

When calling `close_midx()` we not only close the multi-pack index for
one object source, but instead we iterate through the whole linked list
of MIDXs to close all of them. This linked list is about to go away in
favor of using the new per-source pointer to its respective MIDX.

Refactor the function to iterate through sources instead.

Note that after this patch, there's a couple of callsites left that
continue to use `close_midx()` without iterating through all sources.
These are all cases where we don't care about the MIDX from other
sources though, so it's fine to keep them as-is.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

midx.c

@@ -401,7 +401,6 @@ void close_midx(struct multi_pack_index *m)
 	if (!m)
 		return;
 
-	close_midx(m->next);
 	close_midx(m->base_midx);
 
 	munmap((unsigned char *)m->data, m->data_len);
@@ -835,11 +834,15 @@ void clear_midx_file(struct repository *r)
 
 	get_midx_filename(r->hash_algo, &midx, r->objects->sources->path);
 
-	if (r->objects && r->objects->multi_pack_index) {
-		close_midx(r->objects->multi_pack_index);
-		r->objects->multi_pack_index = NULL;
-		for (struct odb_source *source = r->objects->sources; source; source = source->next)
+	if (r->objects) {
+		struct odb_source *source;
+
+		for (source = r->objects->sources; source; source = source->next) {
+			if (source->midx)
+				close_midx(source->midx);
 			source->midx = NULL;
+		}
+		r->objects->multi_pack_index = NULL;
 	}
 
 	if (remove_path(midx.buf))

packfile.c

@@ -361,6 +361,7 @@ void close_pack(struct packed_git *p)
 
 void close_object_store(struct object_database *o)
 {
+	struct odb_source *source;
 	struct packed_git *p;
 
 	for (p = o->packed_git; p; p = p->next)
@@ -369,12 +370,12 @@ void close_object_store(struct object_database *o)
 		else
 			close_pack(p);
 
-	if (o->multi_pack_index) {
-		close_midx(o->multi_pack_index);
-		o->multi_pack_index = NULL;
-		for (struct odb_source *source = o->sources; source; source = source->next)
-			source->midx = NULL;
+	for (source = o->sources; source; source = source->next) {
+		if (source->midx)
+			close_midx(source->midx);
+		source->midx = NULL;
 	}
+	o->multi_pack_index = NULL;
 
 	close_commit_graph(o);
 }