fetch-pack: do not check links for partial fetch

When doing a partial clone or fetch with transfer.fsckobjects=1, use the
--fsck-objects instead of the --strict flag when invoking index-pack so
that links are not checked, only objects. This is because incomplete
links are expected when doing a partial clone or fetch.

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

fetch-pack.c

@@ -886,8 +886,17 @@ static int get_pack(struct fetch_pack_args *args,
 	    ? fetch_fsck_objects
 	    : transfer_fsck_objects >= 0
 	    ? transfer_fsck_objects
-	    : 0)
+	    : 0) {
+		if (args->from_promisor)
+			/*
+			 * We cannot use --strict in index-pack because it
+			 * checks both broken objects and links, but we only
+			 * want to check for broken objects.
+			 */
+			argv_array_push(&cmd.args, "--fsck-objects");
+		else
 			argv_array_push(&cmd.args, "--strict");
+	}
 
 	cmd.in = demux.out;
 	cmd.git_cmd = 1;

t/t5616-partial-clone.sh

@@ -143,4 +143,15 @@ test_expect_success 'manual prefetch of missing objects' '
 	test_line_count = 0 observed.oids
 '
 
+test_expect_success 'partial clone with transfer.fsckobjects=1 uses index-pack --fsck-objects' '
+	git init src &&
+	test_commit -C src x &&
+	test_config -C src uploadpack.allowfilter 1 &&
+	test_config -C src uploadpack.allowanysha1inwant 1 &&
+
+	GIT_TRACE="$(pwd)/trace" git -c transfer.fsckobjects=1 \
+		clone --filter="blob:none" "file://$(pwd)/src" dst &&
+	grep "git index-pack.*--fsck-objects" trace
+'
+
 test_done