[RFC PATCH 1/7] fetch-pack: allow NULL negotiator->add_tip

[Jonathan Tan <jonathantanmy@google.com>]

In a subsequent patch, a null fetch negotiator will be introduced. This
negotiator, among other things, will not need any tip information and
will have a NULL add_tip.

Teach fetch-pack to allow this, and to take advantage of this by
avoiding a ref and alternate traversal when it can. To do this, this
patch combines all invocations of functions that invoke add_tip into one
function, and that function first checks whether add_tip is NULL.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 80fb3bd899..6c786f5970 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -240,6 +240,16 @@ static void mark_tips(struct fetch_negotiator *negotiator,
 	return;
 }
 
+static void add_tips_and_alternates(struct fetch_negotiator *negotiator,
+				    const struct oid_array *negotiation_tips)
+{
+	if (!negotiator->add_tip)
+		return;
+
+	mark_tips(negotiator, negotiation_tips);
+	for_each_cached_alternate(negotiator, insert_one_alternate_object);
+}
+
 static int find_common(struct fetch_negotiator *negotiator,
 		       struct fetch_pack_args *args,
 		       int fd[2], struct object_id *result_oid,
@@ -262,10 +272,8 @@ static int find_common(struct fetch_negotiator *negotiator,
 			   PACKET_READ_CHOMP_NEWLINE |
 			   PACKET_READ_DIE_ON_ERR_PACKET);
 
-	if (!args->no_dependents) {
-		mark_tips(negotiator, args->negotiation_tips);
-		for_each_cached_alternate(negotiator, insert_one_alternate_object);
-	}
+	if (!args->no_dependents)
+		add_tips_and_alternates(negotiator, args->negotiation_tips);
 
 	fetching = 0;
 	for ( ; refs ; refs = refs->next) {
@@ -1575,9 +1583,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				else
 					state = FETCH_SEND_REQUEST;
 
-				mark_tips(negotiator, args->negotiation_tips);
-				for_each_cached_alternate(negotiator,
-							  insert_one_alternate_object);
+				add_tips_and_alternates(negotiator, args->negotiation_tips);
 			} else {
 				filter_refs(args, &ref, sought, nr_sought);
 				state = FETCH_SEND_REQUEST;
-- 
2.28.0.163.g6104cc2f0b6-goog