[PATCH 2/6] fetch-pack: add partial clone refiltering

["Robert Coup via GitGitGadget" <gitgitgadget@gmail.com>]

From: Robert Coup <robert@coup.net.nz>

Allow refetching with a new partial clone filter by not attempting to
find or negotiate common commits with the remote, and always forcing
a full filtered fetch.

Signed-off-by: Robert Coup <robert@coup.net.nz>
---
 fetch-pack.c | 57 ++++++++++++++++++++++++++++++++++------------------
 fetch-pack.h |  1 +
 2 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index dd6ec449f2d..dd670441656 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -312,19 +312,21 @@ static int find_common(struct fetch_negotiator *negotiator,
 		const char *remote_hex;
 		struct object *o;
 
-		/*
-		 * If that object is complete (i.e. it is an ancestor of a
-		 * local ref), we tell them we have it but do not have to
-		 * tell them about its ancestors, which they already know
-		 * about.
-		 *
-		 * We use lookup_object here because we are only
-		 * interested in the case we *know* the object is
-		 * reachable and we have already scanned it.
-		 */
-		if (((o = lookup_object(the_repository, remote)) != NULL) &&
-				(o->flags & COMPLETE)) {
-			continue;
+		if (!args->refilter) {
+			/*
+			* If that object is complete (i.e. it is an ancestor of a
+			* local ref), we tell them we have it but do not have to
+			* tell them about its ancestors, which they already know
+			* about.
+			*
+			* We use lookup_object here because we are only
+			* interested in the case we *know* the object is
+			* reachable and we have already scanned it.
+			*/
+			if (((o = lookup_object(the_repository, remote)) != NULL) &&
+					(o->flags & COMPLETE)) {
+				continue;
+			}
 		}
 
 		remote_hex = oid_to_hex(remote);
@@ -694,6 +696,9 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator,
 
 	save_commit_buffer = 0;
 
+	if (args->refilter)
+		return;
+
 	trace2_region_enter("fetch-pack", "parse_remote_refs_and_find_cutoff", NULL);
 	for (ref = *refs; ref; ref = ref->next) {
 		struct object *o;
@@ -1022,9 +1027,7 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	int agent_len;
 	struct fetch_negotiator negotiator_alloc;
 	struct fetch_negotiator *negotiator;
-
-	negotiator = &negotiator_alloc;
-	fetch_negotiator_init(r, negotiator);
+	unsigned is_refiltering = 0;
 
 	sort_ref_list(&ref, ref_compare_name);
 	QSORT(sought, nr_sought, cmp_ref_by_name);
@@ -1094,10 +1097,14 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	if (server_supports("filter")) {
 		server_supports_filtering = 1;
 		print_verbose(args, _("Server supports %s"), "filter");
-	} else if (args->filter_options.choice) {
+	} else if (args->filter_options.choice || args->refilter) {
 		warning("filtering not recognized by server, ignoring");
 	}
 
+	if (server_supports_filtering && args->refilter) {
+		is_refiltering = 1;
+	}
+
 	if (server_supports("deepen-since")) {
 		print_verbose(args, _("Server supports %s"), "deepen-since");
 		deepen_since_ok = 1;
@@ -1115,9 +1122,16 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	if (!server_supports_hash(the_hash_algo->name, NULL))
 		die(_("Server does not support this repository's object format"));
 
+	negotiator = &negotiator_alloc;
+	if (is_refiltering) {
+		fetch_negotiator_init_noop(negotiator);
+	} else {
+		fetch_negotiator_init(r, negotiator);
+	}
+
 	mark_complete_and_common_ref(negotiator, args, &ref);
 	filter_refs(args, &ref, sought, nr_sought);
-	if (everything_local(args, &ref)) {
+	if (!is_refiltering && everything_local(args, &ref)) {
 		packet_flush(fd[1]);
 		goto all_done;
 	}
@@ -1575,7 +1589,10 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 	struct strvec index_pack_args = STRVEC_INIT;
 
 	negotiator = &negotiator_alloc;
-	fetch_negotiator_init(r, negotiator);
+	if (args->refilter)
+		fetch_negotiator_init_noop(negotiator);
+	else
+		fetch_negotiator_init(r, negotiator);
 
 	packet_reader_init(&reader, fd[0], NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
@@ -1601,7 +1618,7 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 			/* Filter 'ref' by 'sought' and those that aren't local */
 			mark_complete_and_common_ref(negotiator, args, &ref);
 			filter_refs(args, &ref, sought, nr_sought);
-			if (everything_local(args, &ref))
+			if (!args->refilter && everything_local(args, &ref))
 				state = FETCH_DONE;
 			else
 				state = FETCH_SEND_REQUEST;
diff --git a/fetch-pack.h b/fetch-pack.h
index 7f94a2a5831..68df2230c55 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -42,6 +42,7 @@ struct fetch_pack_args {
 	unsigned update_shallow:1;
 	unsigned reject_shallow_remote:1;
 	unsigned deepen:1;
+	unsigned refilter:1;
 
 	/*
 	 * Indicate that the remote of this request is a promisor remote. The
-- 
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