diff --git a/Documentation/git-multi-pack-index.txt b/Documentation/git-multi-pack-index.txt
index eb0caa0439..dd14eab781 100644
--- a/Documentation/git-multi-pack-index.txt
+++ b/Documentation/git-multi-pack-index.txt
@@ -9,7 +9,8 @@ git-multi-pack-index - Write and verify multi-pack-indexes
 SYNOPSIS
 --------
 [verse]
-'git multi-pack-index' [--object-dir=<dir>] [--[no-]progress] <subcommand>
+'git multi-pack-index' [--object-dir=<dir>] [--[no-]progress]
+	[--preferred-pack=<pack>] <subcommand>
 
 DESCRIPTION
 -----------
@@ -27,6 +28,14 @@ OPTIONS
 	Turn progress on/off explicitly. If neither is specified, progress is
 	shown if standard error is connected to a terminal.
 
+--preferred-pack=<pack>::
+	When using the `write` subcommand, optionally specify the
+	tie-breaking pack used when multiple packs contain the same
+	object. Incompatible with other subcommands, including `repack`,
+	which may repack the pack marked as preferred. If not given, the
+	preferred pack is inferred from an existing `multi-pack-index`,
+	if one exists, otherwise the pack with the lowest mtime.
+
 The following subcommands are available:
 
 write::
diff --git a/Documentation/technical/multi-pack-index.txt b/Documentation/technical/multi-pack-index.txt
index e8e377a59f..fb688976c4 100644
--- a/Documentation/technical/multi-pack-index.txt
+++ b/Documentation/technical/multi-pack-index.txt
@@ -43,8 +43,9 @@ Design Details
   a change in format.
 
 - The MIDX keeps only one record per object ID. If an object appears
-  in multiple packfiles, then the MIDX selects the copy in the most-
-  recently modified packfile.
+  in multiple packfiles, then the MIDX selects the copy in the
+  preferred packfile, otherwise selecting from the most-recently
+  modified packfile.
 
 - If there exist packfiles in the pack directory not registered in
   the MIDX, then those packfiles are loaded into the `packed_git`
diff --git a/builtin/multi-pack-index.c b/builtin/multi-pack-index.c
index 5bf88cd2a8..4d1ea3fe84 100644
--- a/builtin/multi-pack-index.c
+++ b/builtin/multi-pack-index.c
@@ -4,6 +4,7 @@
 #include "parse-options.h"
 #include "midx.h"
 #include "trace2.h"
+#include "object-store.h"
 
 static char const * const builtin_multi_pack_index_usage[] = {
 	N_("git multi-pack-index [<options>] (write|verify|expire|repack --batch-size=<size>)"),
@@ -12,6 +13,7 @@ static char const * const builtin_multi_pack_index_usage[] = {
 
 static struct opts_multi_pack_index {
 	const char *object_dir;
+	const char *preferred_pack;
 	unsigned long batch_size;
 	int progress;
 } opts;
@@ -24,6 +26,8 @@ int cmd_multi_pack_index(int argc, const char **argv,
 	static struct option builtin_multi_pack_index_options[] = {
 		OPT_FILENAME(0, "object-dir", &opts.object_dir,
 		  N_("object directory containing set of packfile and pack-index pairs")),
+		OPT_STRING(0, "preferred-pack", &opts.preferred_pack, N_("preferred-pack"),
+		  N_("pack for reuse when computing a multi-pack bitmap")),
 		OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
 		OPT_MAGNITUDE(0, "batch-size", &opts.batch_size,
 		  N_("during repack, collect pack-files of smaller size into a batch that is larger than this size")),
@@ -51,6 +55,9 @@ int cmd_multi_pack_index(int argc, const char **argv,
 		return 1;
 	}
 
+	if (strcmp(argv[0], "write") && opts.preferred_pack)
+		die(_("'--preferred-pack' requires 'write'"));
+
 	trace2_cmd_mode(argv[0]);
 
 	if (!strcmp(argv[0], "repack"))
@@ -60,7 +67,8 @@ int cmd_multi_pack_index(int argc, const char **argv,
 		die(_("--batch-size option is only for 'repack' subcommand"));
 
 	if (!strcmp(argv[0], "write"))
-		return write_midx_file(opts.object_dir, flags);
+		return write_midx_file(opts.object_dir, opts.preferred_pack,
+				       flags);
 	if (!strcmp(argv[0], "verify"))
 		return verify_midx_file(the_repository, opts.object_dir, flags);
 	if (!strcmp(argv[0], "expire"))
diff --git a/builtin/repack.c b/builtin/repack.c
index 01440de2d5..9f00806805 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -523,7 +523,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	remove_temporary_files();
 
 	if (git_env_bool(GIT_TEST_MULTI_PACK_INDEX, 0))
-		write_midx_file(get_object_directory(), 0);
+		write_midx_file(get_object_directory(), NULL, 0);
 
 	string_list_clear(&names, 0);
 	string_list_clear(&rollback, 0);
diff --git a/midx.c b/midx.c
index 05c40a98e0..064670c0c0 100644
--- a/midx.c
+++ b/midx.c
@@ -451,6 +451,24 @@ static int pack_info_compare(const void *_a, const void *_b)
 	return strcmp(a->pack_name, b->pack_name);
 }
 
+static int lookup_idx_or_pack_name(struct pack_info *info,
+				   uint32_t nr,
+				   const char *pack_name)
+{
+	uint32_t lo = 0, hi = nr;
+	while (lo < hi) {
+		uint32_t mi = lo + (hi - lo) / 2;
+		int cmp = cmp_idx_or_pack_name(pack_name, info[mi].pack_name);
+		if (cmp < 0)
+			hi = mi;
+		else if (cmp > 0)
+			lo = mi + 1;
+		else
+			return mi;
+	}
+	return -1;
+}
+
 struct pack_list {
 	struct pack_info *info;
 	uint32_t nr;
@@ -502,6 +520,7 @@ struct pack_midx_entry {
 	uint32_t pack_int_id;
 	time_t pack_mtime;
 	uint64_t offset;
+	unsigned preferred : 1;
 };
 
 static int midx_oid_compare(const void *_a, const void *_b)
@@ -513,6 +532,12 @@ static int midx_oid_compare(const void *_a, const void *_b)
 	if (cmp)
 		return cmp;
 
+	/* Sort objects in a preferred pack first when multiple copies exist. */
+	if (a->preferred > b->preferred)
+		return -1;
+	if (a->preferred < b->preferred)
+		return 1;
+
 	if (a->pack_mtime > b->pack_mtime)
 		return -1;
 	else if (a->pack_mtime < b->pack_mtime)
@@ -540,7 +565,8 @@ static int nth_midxed_pack_midx_entry(struct multi_pack_index *m,
 static void fill_pack_entry(uint32_t pack_int_id,
 			    struct packed_git *p,
 			    uint32_t cur_object,
-			    struct pack_midx_entry *entry)
+			    struct pack_midx_entry *entry,
+			    int preferred)
 {
 	if (nth_packed_object_id(&entry->oid, p, cur_object) < 0)
 		die(_("failed to locate object %d in packfile"), cur_object);
@@ -549,6 +575,7 @@ static void fill_pack_entry(uint32_t pack_int_id,
 	entry->pack_mtime = p->mtime;
 
 	entry->offset = nth_packed_object_offset(p, cur_object);
+	entry->preferred = !!preferred;
 }
 
 /*
@@ -565,7 +592,8 @@ static void fill_pack_entry(uint32_t pack_int_id,
 static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
 						  struct pack_info *info,
 						  uint32_t nr_packs,
-						  uint32_t *nr_objects)
+						  uint32_t *nr_objects,
+						  uint32_t preferred_pack)
 {
 	uint32_t cur_fanout, cur_pack, cur_object;
 	uint32_t alloc_fanout, alloc_objects, total_objects = 0;
@@ -602,12 +630,17 @@ static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
 				nth_midxed_pack_midx_entry(m,
 							   &entries_by_fanout[nr_fanout],
 							   cur_object);
+				if (nth_midxed_pack_int_id(m, cur_object) == preferred_pack)
+					entries_by_fanout[nr_fanout].preferred = 1;
+				else
+					entries_by_fanout[nr_fanout].preferred = 0;
 				nr_fanout++;
 			}
 		}
 
 		for (cur_pack = start_pack; cur_pack < nr_packs; cur_pack++) {
 			uint32_t start = 0, end;
+			int preferred = cur_pack == preferred_pack;
 
 			if (cur_fanout)
 				start = get_pack_fanout(info[cur_pack].p, cur_fanout - 1);
@@ -615,7 +648,11 @@ static struct pack_midx_entry *get_sorted_entries(struct multi_pack_index *m,
 
 			for (cur_object = start; cur_object < end; cur_object++) {
 				ALLOC_GROW(entries_by_fanout, nr_fanout + 1, alloc_fanout);
-				fill_pack_entry(cur_pack, info[cur_pack].p, cur_object, &entries_by_fanout[nr_fanout]);
+				fill_pack_entry(cur_pack,
+						info[cur_pack].p,
+						cur_object,
+						&entries_by_fanout[nr_fanout],
+						preferred);
 				nr_fanout++;
 			}
 		}
@@ -794,7 +831,9 @@ static size_t write_midx_large_offsets(struct hashfile *f, uint32_t nr_large_off
 }
 
 static int write_midx_internal(const char *object_dir, struct multi_pack_index *m,
-			       struct string_list *packs_to_drop, unsigned flags)
+			       struct string_list *packs_to_drop,
+			       const char *preferred_pack_name,
+			       unsigned flags)
 {
 	unsigned char cur_chunk, num_chunks = 0;
 	char *midx_name;
@@ -813,6 +852,7 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
 	int pack_name_concat_len = 0;
 	int dropped_packs = 0;
 	int result = 0;
+	int preferred_pack_idx = -1;
 
 	midx_name = get_midx_filename(object_dir);
 	if (safe_create_leading_directories(midx_name))
@@ -853,7 +893,18 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
 	if (packs.m && packs.nr == packs.m->num_packs && !packs_to_drop)
 		goto cleanup;
 
-	entries = get_sorted_entries(packs.m, packs.info, packs.nr, &nr_entries);
+	if (preferred_pack_name) {
+		for (i = 0; i < packs.nr; i++) {
+			if (!cmp_idx_or_pack_name(preferred_pack_name,
+						  packs.info[i].pack_name)) {
+				preferred_pack_idx = i;
+				break;
+			}
+		}
+	}
+
+	entries = get_sorted_entries(packs.m, packs.info, packs.nr, &nr_entries,
+				     preferred_pack_idx);
 
 	for (i = 0; i < nr_entries; i++) {
 		if (entries[i].offset > 0x7fffffff)
@@ -913,6 +964,31 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
 			pack_name_concat_len += strlen(packs.info[i].pack_name) + 1;
 	}
 
+	/*
+	 * Recompute the preferred_pack_idx (if applicable) according to the
+	 * permuted pack order.
+	 */
+	preferred_pack_idx = -1;
+	if (preferred_pack_name) {
+		preferred_pack_idx = lookup_idx_or_pack_name(packs.info,
+							     packs.nr,
+							     preferred_pack_name);
+		if (preferred_pack_idx < 0)
+			warning(_("unknown preferred pack: '%s'"),
+				preferred_pack_name);
+		else {
+			uint32_t orig = packs.info[preferred_pack_idx].orig_pack_int_id;
+			uint32_t perm = pack_perm[orig];
+
+			if (perm == PACK_EXPIRED) {
+				warning(_("preferred pack '%s' is expired"),
+					preferred_pack_name);
+				preferred_pack_idx = -1;
+			} else
+				preferred_pack_idx = perm;
+		}
+	}
+
 	if (pack_name_concat_len % MIDX_CHUNK_ALIGNMENT)
 		pack_name_concat_len += MIDX_CHUNK_ALIGNMENT -
 					(pack_name_concat_len % MIDX_CHUNK_ALIGNMENT);
@@ -1042,9 +1118,12 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
 	return result;
 }
 
-int write_midx_file(const char *object_dir, unsigned flags)
+int write_midx_file(const char *object_dir,
+		    const char *preferred_pack_name,
+		    unsigned flags)
 {
-	return write_midx_internal(object_dir, NULL, NULL, flags);
+	return write_midx_internal(object_dir, NULL, NULL, preferred_pack_name,
+				   flags);
 }
 
 void clear_midx_file(struct repository *r)
@@ -1279,7 +1358,7 @@ int expire_midx_packs(struct repository *r, const char *object_dir, unsigned fla
 	free(count);
 
 	if (packs_to_drop.nr)
-		result = write_midx_internal(object_dir, m, &packs_to_drop, flags);
+		result = write_midx_internal(object_dir, m, &packs_to_drop, NULL, flags);
 
 	string_list_clear(&packs_to_drop, 0);
 	return result;
@@ -1468,7 +1547,7 @@ int midx_repack(struct repository *r, const char *object_dir, size_t batch_size,
 		goto cleanup;
 	}
 
-	result = write_midx_internal(object_dir, m, NULL, flags);
+	result = write_midx_internal(object_dir, m, NULL, NULL, flags);
 	m = NULL;
 
 cleanup:
diff --git a/midx.h b/midx.h
index b18cf53bc4..e7fea61109 100644
--- a/midx.h
+++ b/midx.h
@@ -47,7 +47,7 @@ int fill_midx_entry(struct repository *r, const struct object_id *oid, struct pa
 int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name);
 int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local);
 
-int write_midx_file(const char *object_dir, unsigned flags);
+int write_midx_file(const char *object_dir, const char *preferred_pack_name, unsigned flags);
 void clear_midx_file(struct repository *r);
 int verify_midx_file(struct repository *r, const char *object_dir, unsigned flags);
 int expire_midx_packs(struct repository *r, const char *object_dir, unsigned flags);
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index 2fc3aadbd1..9304b33484 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -31,6 +31,14 @@ midx_read_expect () {
 	test_cmp expect actual
 }
 
+midx_expect_object_offset () {
+	OID="$1"
+	OFFSET="$2"
+	OBJECT_DIR="$3"
+	test-tool read-midx --show-objects $OBJECT_DIR >actual &&
+	grep "^$OID $OFFSET" actual
+}
+
 test_expect_success 'setup' '
 	test_oid_cache <<-EOF
 	idxoff sha1:2999
@@ -234,6 +242,37 @@ test_expect_success 'warn on improper hash version' '
 	)
 '
 
+test_expect_success 'midx picks objects from preferred pack' '
+	test_when_finished rm -rf preferred.git &&
+	git init --bare preferred.git &&
+	(
+		cd preferred.git &&
+
+		a=$(echo "a" | git hash-object -w --stdin) &&
+		b=$(echo "b" | git hash-object -w --stdin) &&
+		c=$(echo "c" | git hash-object -w --stdin) &&
+
+		# Set up two packs, duplicating the object "B" at different
+		# offsets.
+		git pack-objects objects/pack/test-AB <<-EOF &&
+		$a
+		$b
+		EOF
+		bc=$(git pack-objects objects/pack/test-BC <<-EOF
+		$b
+		$c
+		EOF
+		) &&
+
+		git multi-pack-index --object-dir=objects \
+			--preferred-pack=test-BC-$bc.idx write 2>err &&
+		test_must_be_empty err &&
+
+		ofs=$(git show-index <objects/pack/test-BC-$bc.idx | grep $b |
+			cut -d" " -f1) &&
+		midx_expect_object_offset $b $ofs objects
+	)
+'
 
 test_expect_success 'verify multi-pack-index success' '
 	git multi-pack-index verify --object-dir=$objdir
