filter_refs(): build refs list as we go

Instead of temporarily storing matched refs to temporary array
"return_refs", simply append them to newlist as we go.  This changes
the order of references in newlist to strictly sorted if "--all" and
"--depth" and named references are all specified, but that usage is
broken anyway (see the last two tests in t5500).

This changes the last test in t5500 from segfaulting into just
emitting a spurious error (this will be fixed in a moment).

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch-pack.c

@@ -537,24 +537,11 @@ static int non_matching_ref(struct string_list_item *item, void *unused)
 
 static void filter_refs(struct ref **refs, struct string_list *sought)
 {
-	struct ref **return_refs;
 	struct ref *newlist = NULL;
 	struct ref **newtail = &newlist;
 	struct ref *ref, *next;
-	struct ref *fastarray[32];
 	int sought_pos;
 
-	if (sought->nr && !args.fetch_all) {
-		if (ARRAY_SIZE(fastarray) < sought->nr)
-			return_refs = xcalloc(sought->nr, sizeof(struct ref *));
-		else {
-			return_refs = fastarray;
-			memset(return_refs, 0, sizeof(struct ref *) * sought->nr);
-		}
-	}
-	else
-		return_refs = NULL;
-
 	sought_pos = 0;
 	for (ref = *refs; ref; ref = next) {
 		next = ref->next;
@@ -575,8 +562,10 @@ static void filter_refs(struct ref **refs, struct string_list *sought)
 				if (cmp < 0) /* definitely do not have it */
 					break;
 				else if (cmp == 0) { /* definitely have it */
-					return_refs[sought_pos] = ref;
 					sought->items[sought_pos++].util = "matched";
+					*newtail = ref;
+					ref->next = NULL;
+					newtail = &ref->next;
 					break;
 				}
 				else /* might have it; keep looking */
@@ -588,20 +577,8 @@ static void filter_refs(struct ref **refs, struct string_list *sought)
 		free(ref);
 	}
 
-	if (!args.fetch_all) {
-		int i;
-		for (i = 0; i < sought->nr; i++) {
-			ref = return_refs[i];
-			if (ref) {
-				*newtail = ref;
-				ref->next = NULL;
-				newtail = &ref->next;
-			}
-		}
-		if (return_refs != fastarray)
-			free(return_refs);
+	if (!args.fetch_all)
 		filter_string_list(sought, 0, non_matching_ref, NULL);
-	}
 	*refs = newlist;
 }