diff --git a/Makefile b/Makefile
index 37fdbb04ef..89f6f93d29 100644
--- a/Makefile
+++ b/Makefile
@@ -36,7 +36,7 @@ PROG=   git-update-cache git-diff-files git-init-db git-write-tree \
 	git-diff-helper git-tar-tree git-local-pull git-write-blob \
 	git-get-tar-commit-id git-mkdelta git-apply git-stripspace \
 	git-cvs2git git-diff-stages git-rev-parse git-patch-id \
-	git-pack-objects
+	git-pack-objects git-unpack-objects
 
 all: $(PROG)
 
@@ -124,6 +124,7 @@ git-diff-stages: diff-stages.c
 git-rev-parse: rev-parse.c
 git-patch-id: patch-id.c
 git-pack-objects: pack-objects.c
+git-unpack-objects: unpack-objects.c
 
 git-http-pull: LIBS += -lcurl
 git-rev-list: LIBS += -lssl
diff --git a/unpack-objects.c b/unpack-objects.c
new file mode 100644
index 0000000000..73d0c2d632
--- /dev/null
+++ b/unpack-objects.c
@@ -0,0 +1,105 @@
+#include "cache.h"
+
+static int nr_entries;
+static const char *base_name;
+static const char unpack_usage[] = "git-unpack-objects basename";
+
+struct pack_entry {
+	unsigned int offset;
+	unsigned char sha1[20];
+};
+
+static struct pack_entry **pack_list;
+
+static void *map_file(const char *suffix, unsigned long *sizep)
+{
+	static char pathname[PATH_MAX];
+	unsigned long len;
+	int fd;
+	struct stat st;
+	void *map;
+
+	len = snprintf(pathname, PATH_MAX, "%s.%s", base_name, suffix);
+	if (len >= PATH_MAX)
+		die("bad pack base-name");
+	fd = open(pathname, O_RDONLY);
+	if (fd < 0 || fstat(fd, &st))
+		die("unable to open '%s'", pathname);
+	len = st.st_size;
+	if (!len)
+		die("bad pack file '%s'", pathname);
+	map = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
+	if (-1 == (int)(long)map)
+		die("unable to mmap '%s'", pathname);
+	close(fd);
+	*sizep = len;
+	return map;
+}
+
+static int sort_by_offset(const void *_a, const void *_b)
+{
+	struct pack_entry *a = *(struct pack_entry **)_a;
+	struct pack_entry *b = *(struct pack_entry **)_b;
+	unsigned int o1, o2;
+
+	o1 = ntohl(a->offset);
+	o2 = ntohl(b->offset);
+	return o1 < o2 ? -1 : 1;
+}
+
+static int check_index(void *index, unsigned long idx_size)
+{
+	unsigned int *array = index;
+	unsigned int nr;
+	int i;
+
+	if (idx_size < 4*256)
+		return error("index file too small");
+	nr = 0;
+	for (i = 0; i < 256; i++) {
+		unsigned int n = ntohl(array[i]);
+		if (n < nr)
+			return error("non-monotonic index");
+		nr = n;
+	}
+	if (idx_size != 4*256 + nr * 24) {
+		printf("idx_size=%d, expected %d (%d)\n", idx_size, 4*256 + nr * 24, nr);
+		return error("wrong index file size");
+	}
+
+	nr_entries = nr;
+	pack_list = xmalloc(nr * sizeof(struct pack_entry *));
+	for (i = 0; i < nr; i++)
+		pack_list[i] = index + 4*256 + i*24;
+
+	qsort(pack_list, nr, sizeof(*pack_list), sort_by_offset);
+
+	printf("%d entries\n", nr);
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int i;
+	unsigned long idx_size, pack_size;
+	void *index, *pack;
+
+	for (i = 1 ; i < argc; i++) {
+		const char *arg = argv[i];
+
+		if (*arg == '-') {
+			/* Maybe we'll have some flags here some day.. */
+			usage(unpack_usage);
+		}
+		if (base_name)
+			usage(unpack_usage);
+		base_name = arg;
+	}
+	if (!base_name)
+		usage(unpack_usage);
+	index = map_file("idx", &idx_size);
+	pack = map_file("pack", &pack_size);
+	if (check_index(index, idx_size) < 0)
+		die("bad index file");
+	return 0;
+}