diff --git a/Documentation/git-pack-objects.adoc b/Documentation/git-pack-objects.adoc
index 7f69ae4855..8f0cecaec9 100644
--- a/Documentation/git-pack-objects.adoc
+++ b/Documentation/git-pack-objects.adoc
@@ -87,13 +87,21 @@ base-name::
 	reference was included in the resulting packfile.  This
 	can be useful to send new tags to native Git clients.
 
---stdin-packs::
+--stdin-packs[=<mode>]::
 	Read the basenames of packfiles (e.g., `pack-1234abcd.pack`)
 	from the standard input, instead of object names or revision
 	arguments. The resulting pack contains all objects listed in the
 	included packs (those not beginning with `^`), excluding any
 	objects listed in the excluded packs (beginning with `^`).
 +
+When `mode` is "follow", objects from packs not listed on stdin receive
+special treatment. Objects within unlisted packs will be included if
+those objects are (1) reachable from the included packs, and (2) not
+found in any excluded packs. This mode is useful, for example, to
+resurrect once-unreachable objects found in cruft packs to generate
+packs which are closed under reachability up to the boundary set by the
+excluded packs.
++
 Incompatible with `--revs`, or options that imply `--revs` (such as
 `--all`), with the exception of `--unpacked`, which is compatible.
 
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index f4009cd391..67a22b2dc4 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -272,6 +272,12 @@ static struct oidmap configured_exclusions;
 static struct oidset excluded_by_config;
 static int name_hash_version = -1;
 
+enum stdin_packs_mode {
+	STDIN_PACKS_MODE_NONE,
+	STDIN_PACKS_MODE_STANDARD,
+	STDIN_PACKS_MODE_FOLLOW,
+};
+
 /**
  * Check whether the name_hash_version chosen by user input is appropriate,
  * and also validate whether it is compatible with other features.
@@ -3514,31 +3520,44 @@ static int add_object_entry_from_pack(const struct object_id *oid,
 }
 
 static void show_object_pack_hint(struct object *object, const char *name,
-				  void *data UNUSED)
+				  void *data)
 {
-	struct object_entry *oe = packlist_find(&to_pack, &object->oid);
-	if (!oe)
-		return;
+	enum stdin_packs_mode mode = *(enum stdin_packs_mode *)data;
+	if (mode == STDIN_PACKS_MODE_FOLLOW) {
+		add_object_entry(&object->oid, object->type, name, 0);
+	} else {
+		struct object_entry *oe = packlist_find(&to_pack, &object->oid);
+		if (!oe)
+			return;
 
-	/*
-	 * Our 'to_pack' list was constructed by iterating all objects packed in
-	 * included packs, and so doesn't have a non-zero hash field that you
-	 * would typically pick up during a reachability traversal.
-	 *
-	 * Make a best-effort attempt to fill in the ->hash and ->no_try_delta
-	 * fields here in order to perhaps improve the delta selection
-	 * process.
-	 */
-	oe->hash = pack_name_hash_fn(name);
-	oe->no_try_delta = name && no_try_delta(name);
+		/*
+		 * Our 'to_pack' list was constructed by iterating all
+		 * objects packed in included packs, and so doesn't have
+		 * a non-zero hash field that you would typically pick
+		 * up during a reachability traversal.
+		 *
+		 * Make a best-effort attempt to fill in the ->hash and
+		 * ->no_try_delta fields here in order to perhaps
+		 * improve the delta selection process.
+		 */
+		oe->hash = pack_name_hash_fn(name);
+		oe->no_try_delta = name && no_try_delta(name);
 
-	stdin_packs_hints_nr++;
+		stdin_packs_hints_nr++;
+	}
 }
 
-static void show_commit_pack_hint(struct commit *commit UNUSED,
-				  void *data UNUSED)
+static void show_commit_pack_hint(struct commit *commit, void *data)
 {
+	enum stdin_packs_mode mode = *(enum stdin_packs_mode *)data;
+
+	if (mode == STDIN_PACKS_MODE_FOLLOW) {
+		show_object_pack_hint((struct object *)commit, "", data);
+		return;
+	}
+
 	/* nothing to do; commits don't have a namehash */
+
 }
 
 static int pack_mtime_cmp(const void *_a, const void *_b)
@@ -3646,7 +3665,7 @@ static void read_packs_list_from_stdin(struct rev_info *revs)
 
 static void add_unreachable_loose_objects(struct rev_info *revs);
 
-static void read_stdin_packs(int rev_list_unpacked)
+static void read_stdin_packs(enum stdin_packs_mode mode, int rev_list_unpacked)
 {
 	struct rev_info revs;
 
@@ -3678,7 +3697,7 @@ static void read_stdin_packs(int rev_list_unpacked)
 	traverse_commit_list(&revs,
 			     show_commit_pack_hint,
 			     show_object_pack_hint,
-			     NULL);
+			     &mode);
 
 	trace2_data_intmax("pack-objects", the_repository, "stdin_packs_found",
 			   stdin_packs_found_nr);
@@ -4469,6 +4488,23 @@ static int is_not_in_promisor_pack(struct commit *commit, void *data) {
 	return is_not_in_promisor_pack_obj((struct object *) commit, data);
 }
 
+static int parse_stdin_packs_mode(const struct option *opt, const char *arg,
+				  int unset)
+{
+	enum stdin_packs_mode *mode = opt->value;
+
+	if (unset)
+		*mode = STDIN_PACKS_MODE_NONE;
+	else if (!arg || !*arg)
+		*mode = STDIN_PACKS_MODE_STANDARD;
+	else if (!strcmp(arg, "follow"))
+		*mode = STDIN_PACKS_MODE_FOLLOW;
+	else
+		die(_("invalid value for '%s': '%s'"), opt->long_name, arg);
+
+	return 0;
+}
+
 int cmd_pack_objects(int argc,
 		     const char **argv,
 		     const char *prefix,
@@ -4480,7 +4516,7 @@ int cmd_pack_objects(int argc,
 	struct strvec rp = STRVEC_INIT;
 	int rev_list_unpacked = 0, rev_list_all = 0, rev_list_reflog = 0;
 	int rev_list_index = 0;
-	int stdin_packs = 0;
+	enum stdin_packs_mode stdin_packs = STDIN_PACKS_MODE_NONE;
 	struct string_list keep_pack_list = STRING_LIST_INIT_NODUP;
 	struct list_objects_filter_options filter_options =
 		LIST_OBJECTS_FILTER_INIT;
@@ -4535,6 +4571,9 @@ int cmd_pack_objects(int argc,
 		OPT_SET_INT_F(0, "indexed-objects", &rev_list_index,
 			      N_("include objects referred to by the index"),
 			      1, PARSE_OPT_NONEG),
+		OPT_CALLBACK_F(0, "stdin-packs", &stdin_packs, N_("mode"),
+			     N_("read packs from stdin"),
+			     PARSE_OPT_OPTARG, parse_stdin_packs_mode),
 		OPT_BOOL(0, "stdin-packs", &stdin_packs,
 			 N_("read packs from stdin")),
 		OPT_BOOL(0, "stdout", &pack_to_stdout,
@@ -4791,7 +4830,7 @@ int cmd_pack_objects(int argc,
 		progress_state = start_progress(the_repository,
 						_("Enumerating objects"), 0);
 	if (stdin_packs) {
-		read_stdin_packs(rev_list_unpacked);
+		read_stdin_packs(stdin_packs, rev_list_unpacked);
 	} else if (cruft) {
 		read_cruft_objects();
 	} else if (!use_internal_rev_list) {
diff --git a/t/t5331-pack-objects-stdin.sh b/t/t5331-pack-objects-stdin.sh
index 8fd07deb8d..60a2b4bc07 100755
--- a/t/t5331-pack-objects-stdin.sh
+++ b/t/t5331-pack-objects-stdin.sh
@@ -236,4 +236,86 @@ test_expect_success 'pack-objects --stdin with packfiles from main and alternate
 	test_cmp expected-objects actual-objects
 '
 
+packdir=.git/objects/pack
+
+objects_in_packs () {
+	for p in "$@"
+	do
+		git show-index <"$packdir/pack-$p.idx" || return 1
+	done >objects.raw &&
+
+	cut -d' ' -f2 objects.raw | sort &&
+	rm -f objects.raw
+}
+
+test_expect_success '--stdin-packs=follow walks into unknown packs' '
+	test_when_finished "rm -fr repo" &&
+
+	git init repo &&
+	(
+		cd repo &&
+
+		for c in A B C D
+		do
+			test_commit "$c" || return 1
+		done &&
+
+		A="$(echo A | git pack-objects --revs $packdir/pack)" &&
+		B="$(echo A..B | git pack-objects --revs $packdir/pack)" &&
+		C="$(echo B..C | git pack-objects --revs $packdir/pack)" &&
+		D="$(echo C..D | git pack-objects --revs $packdir/pack)" &&
+		test_commit E &&
+
+		git prune-packed &&
+
+		cat >in <<-EOF &&
+		pack-$B.pack
+		^pack-$C.pack
+		pack-$D.pack
+		EOF
+
+		# With just --stdin-packs, pack "A" is unknown to us, so
+		# only objects from packs "B" and "D" are included in
+		# the output pack.
+		P=$(git pack-objects --stdin-packs $packdir/pack <in) &&
+		objects_in_packs $B $D >expect &&
+		objects_in_packs $P >actual &&
+		test_cmp expect actual &&
+
+		# But with --stdin-packs=follow, objects from both
+		# included packs reach objects from the unknown pack, so
+		# objects from pack "A" is included in the output pack
+		# in addition to the above.
+		P=$(git pack-objects --stdin-packs=follow $packdir/pack <in) &&
+		objects_in_packs $A $B $D >expect &&
+		objects_in_packs $P >actual &&
+		test_cmp expect actual &&
+
+		# And with --unpacked, we will pick up objects from unknown
+		# packs that are reachable from loose objects. Loose object E
+		# reaches objects in pack A, but there are three excluded packs
+		# in between.
+		#
+		# The resulting pack should include objects reachable from E
+		# that are not present in packs B, C, or D, along with those
+		# present in pack A.
+		cat >in <<-EOF &&
+		^pack-$B.pack
+		^pack-$C.pack
+		^pack-$D.pack
+		EOF
+
+		P=$(git pack-objects --stdin-packs=follow --unpacked \
+			$packdir/pack <in) &&
+
+		{
+			objects_in_packs $A &&
+			git rev-list --objects --no-object-names D..E
+		}>expect.raw &&
+		sort expect.raw >expect &&
+		objects_in_packs $P >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_done
