Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 1849 insertions, 0 deletions

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
new file mode 100644
index 000000000000..0d55f73b0b44
--- /dev/null
+++ b/builtin/index-pack.c
@@ -0,0 +1,1849 @@
+#include "builtin.h"
+#include "config.h"
+#include "delta.h"
+#include "pack.h"
+#include "csum-file.h"
+#include "blob.h"
+#include "commit.h"
+#include "tag.h"
+#include "tree.h"
+#include "progress.h"
+#include "fsck.h"
+#include "exec-cmd.h"
+#include "streaming.h"
+#include "thread-utils.h"
+#include "packfile.h"
+#include "object-store.h"
+#include "fetch-object.h"
+
+static const char index_pack_usage[] =
+"git index-pack [-v] [-o <index-file>] [--keep | --keep=<msg>] [--verify] [--strict] (<pack-file> | --stdin [--fix-thin] [<pack-file>])";
+
+struct object_entry {
+	struct pack_idx_entry idx;
+	unsigned long size;
+	unsigned char hdr_size;
+	signed char type;
+	signed char real_type;
+};
+
+struct object_stat {
+	unsigned delta_depth;
+	int base_object_no;
+};
+
+struct base_data {
+	struct base_data *base;
+	struct base_data *child;
+	struct object_entry *obj;
+	void *data;
+	unsigned long size;
+	int ref_first, ref_last;
+	int ofs_first, ofs_last;
+};
+
+struct thread_local {
+	pthread_t thread;
+	struct base_data *base_cache;
+	size_t base_cache_used;
+	int pack_fd;
+};
+
+/* Remember to update object flag allocation in object.h */
+#define FLAG_LINK (1u<<20)
+#define FLAG_CHECKED (1u<<21)
+
+struct ofs_delta_entry {
+	off_t offset;
+	int obj_no;
+};
+
+struct ref_delta_entry {
+	struct object_id oid;
+	int obj_no;
+};
+
+static struct object_entry *objects;
+static struct object_stat *obj_stat;
+static struct ofs_delta_entry *ofs_deltas;
+static struct ref_delta_entry *ref_deltas;
+static struct thread_local nothread_data;
+static int nr_objects;
+static int nr_ofs_deltas;
+static int nr_ref_deltas;
+static int ref_deltas_alloc;
+static int nr_resolved_deltas;
+static int nr_threads;
+
+static int from_stdin;
+static int strict;
+static int do_fsck_object;
+static struct fsck_options fsck_options = FSCK_OPTIONS_STRICT;
+static int verbose;
+static int show_resolving_progress;
+static int show_stat;
+static int check_self_contained_and_connected;
+
+static struct progress *progress;
+
+/* We always read in 4kB chunks. */
+static unsigned char input_buffer[4096];
+static unsigned int input_offset, input_len;
+static off_t consumed_bytes;
+static off_t max_input_size;
+static unsigned deepest_delta;
+static git_hash_ctx input_ctx;
+static uint32_t input_crc32;
+static int input_fd, output_fd;
+static const char *curr_pack;
+
+static struct thread_local *thread_data;
+static int nr_dispatched;
+static int threads_active;
+
+static pthread_mutex_t read_mutex;
+#define read_lock()		lock_mutex(&read_mutex)
+#define read_unlock()		unlock_mutex(&read_mutex)
+
+static pthread_mutex_t counter_mutex;
+#define counter_lock()		lock_mutex(&counter_mutex)
+#define counter_unlock()	unlock_mutex(&counter_mutex)
+
+static pthread_mutex_t work_mutex;
+#define work_lock()		lock_mutex(&work_mutex)
+#define work_unlock()		unlock_mutex(&work_mutex)
+
+static pthread_mutex_t deepest_delta_mutex;
+#define deepest_delta_lock()	lock_mutex(&deepest_delta_mutex)
+#define deepest_delta_unlock()	unlock_mutex(&deepest_delta_mutex)
+
+static pthread_mutex_t type_cas_mutex;
+#define type_cas_lock()		lock_mutex(&type_cas_mutex)
+#define type_cas_unlock()	unlock_mutex(&type_cas_mutex)
+
+static pthread_key_t key;
+
+static inline void lock_mutex(pthread_mutex_t *mutex)
+{
+	if (threads_active)
+		pthread_mutex_lock(mutex);
+}
+
+static inline void unlock_mutex(pthread_mutex_t *mutex)
+{
+	if (threads_active)
+		pthread_mutex_unlock(mutex);
+}
+
+/*
+ * Mutex and conditional variable can't be statically-initialized on Windows.
+ */
+static void init_thread(void)
+{
+	int i;
+	init_recursive_mutex(&read_mutex);
+	pthread_mutex_init(&counter_mutex, NULL);
+	pthread_mutex_init(&work_mutex, NULL);
+	pthread_mutex_init(&type_cas_mutex, NULL);
+	if (show_stat)
+		pthread_mutex_init(&deepest_delta_mutex, NULL);
+	pthread_key_create(&key, NULL);
+	thread_data = xcalloc(nr_threads, sizeof(*thread_data));
+	for (i = 0; i < nr_threads; i++) {
+		thread_data[i].pack_fd = open(curr_pack, O_RDONLY);
+		if (thread_data[i].pack_fd == -1)
+			die_errno(_("unable to open %s"), curr_pack);
+	}
+
+	threads_active = 1;
+}
+
+static void cleanup_thread(void)
+{
+	int i;
+	if (!threads_active)
+		return;
+	threads_active = 0;
+	pthread_mutex_destroy(&read_mutex);
+	pthread_mutex_destroy(&counter_mutex);
+	pthread_mutex_destroy(&work_mutex);
+	pthread_mutex_destroy(&type_cas_mutex);
+	if (show_stat)
+		pthread_mutex_destroy(&deepest_delta_mutex);
+	for (i = 0; i < nr_threads; i++)
+		close(thread_data[i].pack_fd);
+	pthread_key_delete(key);
+	free(thread_data);
+}
+
+static int mark_link(struct object *obj, int type, void *data, struct fsck_options *options)
+{
+	if (!obj)
+		return -1;
+
+	if (type != OBJ_ANY && obj->type != type)
+		die(_("object type mismatch at %s"), oid_to_hex(&obj->oid));
+
+	obj->flags |= FLAG_LINK;
+	return 0;
+}
+
+/* The content of each linked object must have been checked
+   or it must be already present in the object database */
+static unsigned check_object(struct object *obj)
+{
+	if (!obj)
+		return 0;
+
+	if (!(obj->flags & FLAG_LINK))
+		return 0;
+
+	if (!(obj->flags & FLAG_CHECKED)) {
+		unsigned long size;
+		int type = oid_object_info(the_repository, &obj->oid, &size);
+		if (type <= 0)
+			die(_("did not receive expected object %s"),
+			      oid_to_hex(&obj->oid));
+		if (type != obj->type)
+			die(_("object %s: expected type %s, found %s"),
+			    oid_to_hex(&obj->oid),
+			    type_name(obj->type), type_name(type));
+		obj->flags |= FLAG_CHECKED;
+		return 1;
+	}
+
+	return 0;
+}
+
+static unsigned check_objects(void)
+{
+	unsigned i, max, foreign_nr = 0;
+
+	max = get_max_object_index();
+
+	if (verbose)
+		progress = start_delayed_progress(_("Checking objects"), max);
+
+	for (i = 0; i < max; i++) {
+		foreign_nr += check_object(get_indexed_object(i));
+		display_progress(progress, i + 1);
+	}
+
+	stop_progress(&progress);
+	return foreign_nr;
+}
+
+
+/* Discard current buffer used content. */
+static void flush(void)
+{
+	if (input_offset) {
+		if (output_fd >= 0)
+			write_or_die(output_fd, input_buffer, input_offset);
+		the_hash_algo->update_fn(&input_ctx, input_buffer, input_offset);
+		memmove(input_buffer, input_buffer + input_offset, input_len);
+		input_offset = 0;
+	}
+}
+
+/*
+ * Make sure at least "min" bytes are available in the buffer, and
+ * return the pointer to the buffer.
+ */
+static void *fill(int min)
+{
+	if (min <= input_len)
+		return input_buffer + input_offset;
+	if (min > sizeof(input_buffer))
+		die(Q_("cannot fill %d byte",
+		       "cannot fill %d bytes",
+		       min),
+		    min);
+	flush();
+	do {
+		ssize_t ret = xread(input_fd, input_buffer + input_len,
+				sizeof(input_buffer) - input_len);
+		if (ret <= 0) {
+			if (!ret)
+				die(_("early EOF"));
+			die_errno(_("read error on input"));
+		}
+		input_len += ret;
+		if (from_stdin)
+			display_throughput(progress, consumed_bytes + input_len);
+	} while (input_len < min);
+	return input_buffer;
+}
+
+static void use(int bytes)
+{
+	if (bytes > input_len)
+		die(_("used more bytes than were available"));
+	input_crc32 = crc32(input_crc32, input_buffer + input_offset, bytes);
+	input_len -= bytes;
+	input_offset += bytes;
+
+	/* make sure off_t is sufficiently large not to wrap */
+	if (signed_add_overflows(consumed_bytes, bytes))
+		die(_("pack too large for current definition of off_t"));
+	consumed_bytes += bytes;
+	if (max_input_size && consumed_bytes > max_input_size)
+		die(_("pack exceeds maximum allowed size"));
+}
+
+static const char *open_pack_file(const char *pack_name)
+{
+	if (from_stdin) {
+		input_fd = 0;
+		if (!pack_name) {
+			struct strbuf tmp_file = STRBUF_INIT;
+			output_fd = odb_mkstemp(&tmp_file,
+						"pack/tmp_pack_XXXXXX");
+			pack_name = strbuf_detach(&tmp_file, NULL);
+		} else {
+			output_fd = open(pack_name, O_CREAT|O_EXCL|O_RDWR, 0600);
+			if (output_fd < 0)
+				die_errno(_("unable to create '%s'"), pack_name);
+		}
+		nothread_data.pack_fd = output_fd;
+	} else {
+		input_fd = open(pack_name, O_RDONLY);
+		if (input_fd < 0)
+			die_errno(_("cannot open packfile '%s'"), pack_name);
+		output_fd = -1;
+		nothread_data.pack_fd = input_fd;
+	}
+	the_hash_algo->init_fn(&input_ctx);
+	return pack_name;
+}
+
+static void parse_pack_header(void)
+{
+	struct pack_header *hdr = fill(sizeof(struct pack_header));
+
+	/* Header consistency check */
+	if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
+		die(_("pack signature mismatch"));
+	if (!pack_version_ok(hdr->hdr_version))
+		die(_("pack version %"PRIu32" unsupported"),
+			ntohl(hdr->hdr_version));
+
+	nr_objects = ntohl(hdr->hdr_entries);
+	use(sizeof(struct pack_header));
+}
+
+static NORETURN void bad_object(off_t offset, const char *format,
+		       ...) __attribute__((format (printf, 2, 3)));
+
+static NORETURN void bad_object(off_t offset, const char *format, ...)
+{
+	va_list params;
+	char buf[1024];
+
+	va_start(params, format);
+	vsnprintf(buf, sizeof(buf), format, params);
+	va_end(params);
+	die(_("pack has bad object at offset %"PRIuMAX": %s"),
+	    (uintmax_t)offset, buf);
+}
+
+static inline struct thread_local *get_thread_data(void)
+{
+	if (HAVE_THREADS) {
+		if (threads_active)
+			return pthread_getspecific(key);
+		assert(!threads_active &&
+		       "This should only be reached when all threads are gone");
+	}
+	return &nothread_data;
+}
+
+static void set_thread_data(struct thread_local *data)
+{
+	if (threads_active)
+		pthread_setspecific(key, data);
+}
+
+static struct base_data *alloc_base_data(void)
+{
+	struct base_data *base = xcalloc(1, sizeof(struct base_data));
+	base->ref_last = -1;
+	base->ofs_last = -1;
+	return base;
+}
+
+static void free_base_data(struct base_data *c)
+{
+	if (c->data) {
+		FREE_AND_NULL(c->data);
+		get_thread_data()->base_cache_used -= c->size;
+	}
+}
+
+static void prune_base_data(struct base_data *retain)
+{
+	struct base_data *b;
+	struct thread_local *data = get_thread_data();
+	for (b = data->base_cache;
+	     data->base_cache_used > delta_base_cache_limit && b;
+	     b = b->child) {
+		if (b->data && b != retain)
+			free_base_data(b);
+	}
+}
+
+static void link_base_data(struct base_data *base, struct base_data *c)
+{
+	if (base)
+		base->child = c;
+	else
+		get_thread_data()->base_cache = c;
+
+	c->base = base;
+	c->child = NULL;
+	if (c->data)
+		get_thread_data()->base_cache_used += c->size;
+	prune_base_data(c);
+}
+
+static void unlink_base_data(struct base_data *c)
+{
+	struct base_data *base = c->base;
+	if (base)
+		base->child = NULL;
+	else
+		get_thread_data()->base_cache = NULL;
+	free_base_data(c);
+}
+
+static int is_delta_type(enum object_type type)
+{
+	return (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA);
+}
+
+static void *unpack_entry_data(off_t offset, unsigned long size,
+			       enum object_type type, struct object_id *oid)
+{
+	static char fixed_buf[8192];
+	int status;
+	git_zstream stream;
+	void *buf;
+	git_hash_ctx c;
+	char hdr[32];
+	int hdrlen;
+
+	if (!is_delta_type(type)) {
+		hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %"PRIuMAX,
+				   type_name(type),(uintmax_t)size) + 1;
+		the_hash_algo->init_fn(&c);
+		the_hash_algo->update_fn(&c, hdr, hdrlen);
+	} else
+		oid = NULL;
+	if (type == OBJ_BLOB && size > big_file_threshold)
+		buf = fixed_buf;
+	else
+		buf = xmallocz(size);
+
+	memset(&stream, 0, sizeof(stream));
+	git_inflate_init(&stream);
+	stream.next_out = buf;
+	stream.avail_out = buf == fixed_buf ? sizeof(fixed_buf) : size;
+
+	do {
+		unsigned char *last_out = stream.next_out;
+		stream.next_in = fill(1);
+		stream.avail_in = input_len;
+		status = git_inflate(&stream, 0);
+		use(input_len - stream.avail_in);
+		if (oid)
+			the_hash_algo->update_fn(&c, last_out, stream.next_out - last_out);
+		if (buf == fixed_buf) {
+			stream.next_out = buf;
+			stream.avail_out = sizeof(fixed_buf);
+		}
+	} while (status == Z_OK);
+	if (stream.total_out != size || status != Z_STREAM_END)
+		bad_object(offset, _("inflate returned %d"), status);
+	git_inflate_end(&stream);
+	if (oid)
+		the_hash_algo->final_fn(oid->hash, &c);
+	return buf == fixed_buf ? NULL : buf;
+}
+
+static void *unpack_raw_entry(struct object_entry *obj,
+			      off_t *ofs_offset,
+			      struct object_id *ref_oid,
+			      struct object_id *oid)
+{
+	unsigned char *p;
+	unsigned long size, c;
+	off_t base_offset;
+	unsigned shift;
+	void *data;
+
+	obj->idx.offset = consumed_bytes;
+	input_crc32 = crc32(0, NULL, 0);
+
+	p = fill(1);
+	c = *p;
+	use(1);
+	obj->type = (c >> 4) & 7;
+	size = (c & 15);
+	shift = 4;
+	while (c & 0x80) {
+		p = fill(1);
+		c = *p;
+		use(1);
+		size += (c & 0x7f) << shift;
+		shift += 7;
+	}
+	obj->size = size;
+
+	switch (obj->type) {
+	case OBJ_REF_DELTA:
+		hashcpy(ref_oid->hash, fill(the_hash_algo->rawsz));
+		use(the_hash_algo->rawsz);
+		break;
+	case OBJ_OFS_DELTA:
+		p = fill(1);
+		c = *p;
+		use(1);
+		base_offset = c & 127;
+		while (c & 128) {
+			base_offset += 1;
+			if (!base_offset || MSB(base_offset, 7))
+				bad_object(obj->idx.offset, _("offset value overflow for delta base object"));
+			p = fill(1);
+			c = *p;
+			use(1);
+			base_offset = (base_offset << 7) + (c & 127);
+		}
+		*ofs_offset = obj->idx.offset - base_offset;
+		if (*ofs_offset <= 0 || *ofs_offset >= obj->idx.offset)
+			bad_object(obj->idx.offset, _("delta base offset is out of bound"));
+		break;
+	case OBJ_COMMIT:
+	case OBJ_TREE:
+	case OBJ_BLOB:
+	case OBJ_TAG:
+		break;
+	default:
+		bad_object(obj->idx.offset, _("unknown object type %d"), obj->type);
+	}
+	obj->hdr_size = consumed_bytes - obj->idx.offset;
+
+	data = unpack_entry_data(obj->idx.offset, obj->size, obj->type, oid);
+	obj->idx.crc32 = input_crc32;
+	return data;
+}
+
+static void *unpack_data(struct object_entry *obj,
+			 int (*consume)(const unsigned char *, unsigned long, void *),
+			 void *cb_data)
+{
+	off_t from = obj[0].idx.offset + obj[0].hdr_size;
+	off_t len = obj[1].idx.offset - from;
+	unsigned char *data, *inbuf;
+	git_zstream stream;
+	int status;
+
+	data = xmallocz(consume ? 64*1024 : obj->size);
+	inbuf = xmalloc((len < 64*1024) ? (int)len : 64*1024);
+
+	memset(&stream, 0, sizeof(stream));
+	git_inflate_init(&stream);
+	stream.next_out = data;
+	stream.avail_out = consume ? 64*1024 : obj->size;
+
+	do {
+		ssize_t n = (len < 64*1024) ? (ssize_t)len : 64*1024;
+		n = xpread(get_thread_data()->pack_fd, inbuf, n, from);
+		if (n < 0)
+			die_errno(_("cannot pread pack file"));
+		if (!n)
+			die(Q_("premature end of pack file, %"PRIuMAX" byte missing",
+			       "premature end of pack file, %"PRIuMAX" bytes missing",
+			       (unsigned int)len),
+			    (uintmax_t)len);
+		from += n;
+		len -= n;
+		stream.next_in = inbuf;
+		stream.avail_in = n;
+		if (!consume)
+			status = git_inflate(&stream, 0);
+		else {
+			do {
+				status = git_inflate(&stream, 0);
+				if (consume(data, stream.next_out - data, cb_data)) {
+					free(inbuf);
+					free(data);
+					return NULL;
+				}
+				stream.next_out = data;
+				stream.avail_out = 64*1024;
+			} while (status == Z_OK && stream.avail_in);
+		}
+	} while (len && status == Z_OK && !stream.avail_in);
+
+	/* This has been inflated OK when first encountered, so... */
+	if (status != Z_STREAM_END || stream.total_out != obj->size)
+		die(_("serious inflate inconsistency"));
+
+	git_inflate_end(&stream);
+	free(inbuf);
+	if (consume) {
+		FREE_AND_NULL(data);
+	}
+	return data;
+}
+
+static void *get_data_from_pack(struct object_entry *obj)
+{
+	return unpack_data(obj, NULL, NULL);
+}
+
+static int compare_ofs_delta_bases(off_t offset1, off_t offset2,
+				   enum object_type type1,
+				   enum object_type type2)
+{
+	int cmp = type1 - type2;
+	if (cmp)
+		return cmp;
+	return offset1 < offset2 ? -1 :
+	       offset1 > offset2 ?  1 :
+	       0;
+}
+
+static int find_ofs_delta(const off_t offset, enum object_type type)
+{
+	int first = 0, last = nr_ofs_deltas;
+
+	while (first < last) {
+		int next = first + (last - first) / 2;
+		struct ofs_delta_entry *delta = &ofs_deltas[next];
+		int cmp;
+
+		cmp = compare_ofs_delta_bases(offset, delta->offset,
+					      type, objects[delta->obj_no].type);
+		if (!cmp)
+			return next;
+		if (cmp < 0) {
+			last = next;
+			continue;
+		}
+		first = next+1;
+	}
+	return -first-1;
+}
+
+static void find_ofs_delta_children(off_t offset,
+				    int *first_index, int *last_index,
+				    enum object_type type)
+{
+	int first = find_ofs_delta(offset, type);
+	int last = first;
+	int end = nr_ofs_deltas - 1;
+
+	if (first < 0) {
+		*first_index = 0;
+		*last_index = -1;
+		return;
+	}
+	while (first > 0 && ofs_deltas[first - 1].offset == offset)
+		--first;
+	while (last < end && ofs_deltas[last + 1].offset == offset)
+		++last;
+	*first_index = first;
+	*last_index = last;
+}
+
+static int compare_ref_delta_bases(const struct object_id *oid1,
+				   const struct object_id *oid2,
+				   enum object_type type1,
+				   enum object_type type2)
+{
+	int cmp = type1 - type2;
+	if (cmp)
+		return cmp;
+	return oidcmp(oid1, oid2);
+}
+
+static int find_ref_delta(const struct object_id *oid, enum object_type type)
+{
+	int first = 0, last = nr_ref_deltas;
+
+	while (first < last) {
+		int next = first + (last - first) / 2;
+		struct ref_delta_entry *delta = &ref_deltas[next];
+		int cmp;
+
+		cmp = compare_ref_delta_bases(oid, &delta->oid,
+					      type, objects[delta->obj_no].type);
+		if (!cmp)
+			return next;
+		if (cmp < 0) {
+			last = next;
+			continue;
+		}
+		first = next+1;
+	}
+	return -first-1;
+}
+
+static void find_ref_delta_children(const struct object_id *oid,
+				    int *first_index, int *last_index,
+				    enum object_type type)
+{
+	int first = find_ref_delta(oid, type);
+	int last = first;
+	int end = nr_ref_deltas - 1;
+
+	if (first < 0) {
+		*first_index = 0;
+		*last_index = -1;
+		return;
+	}
+	while (first > 0 && oideq(&ref_deltas[first - 1].oid, oid))
+		--first;
+	while (last < end && oideq(&ref_deltas[last + 1].oid, oid))
+		++last;
+	*first_index = first;
+	*last_index = last;
+}
+
+struct compare_data {
+	struct object_entry *entry;
+	struct git_istream *st;
+	unsigned char *buf;
+	unsigned long buf_size;
+};
+
+static int compare_objects(const unsigned char *buf, unsigned long size,
+			   void *cb_data)
+{
+	struct compare_data *data = cb_data;
+
+	if (data->buf_size < size) {
+		free(data->buf);
+		data->buf = xmalloc(size);
+		data->buf_size = size;
+	}
+
+	while (size) {
+		ssize_t len = read_istream(data->st, data->buf, size);
+		if (len == 0)
+			die(_("SHA1 COLLISION FOUND WITH %s !"),
+			    oid_to_hex(&data->entry->idx.oid));
+		if (len < 0)
+			die(_("unable to read %s"),
+			    oid_to_hex(&data->entry->idx.oid));
+		if (memcmp(buf, data->buf, len))
+			die(_("SHA1 COLLISION FOUND WITH %s !"),
+			    oid_to_hex(&data->entry->idx.oid));
+		size -= len;
+		buf += len;
+	}
+	return 0;
+}
+
+static int check_collison(struct object_entry *entry)
+{
+	struct compare_data data;
+	enum object_type type;
+	unsigned long size;
+
+	if (entry->size <= big_file_threshold || entry->type != OBJ_BLOB)
+		return -1;
+
+	memset(&data, 0, sizeof(data));
+	data.entry = entry;
+	data.st = open_istream(&entry->idx.oid, &type, &size, NULL);
+	if (!data.st)
+		return -1;
+	if (size != entry->size || type != entry->type)
+		die(_("SHA1 COLLISION FOUND WITH %s !"),
+		    oid_to_hex(&entry->idx.oid));
+	unpack_data(entry, compare_objects, &data);
+	close_istream(data.st);
+	free(data.buf);
+	return 0;
+}
+
+static void sha1_object(const void *data, struct object_entry *obj_entry,
+			unsigned long size, enum object_type type,
+			const struct object_id *oid)
+{
+	void *new_data = NULL;
+	int collision_test_needed = 0;
+
+	assert(data || obj_entry);
+
+	if (startup_info->have_repository) {
+		read_lock();
+		collision_test_needed =
+			has_object_file_with_flags(oid, OBJECT_INFO_QUICK);
+		read_unlock();
+	}
+
+	if (collision_test_needed && !data) {
+		read_lock();
+		if (!check_collison(obj_entry))
+			collision_test_needed = 0;
+		read_unlock();
+	}
+	if (collision_test_needed) {
+		void *has_data;
+		enum object_type has_type;
+		unsigned long has_size;
+		read_lock();
+		has_type = oid_object_info(the_repository, oid, &has_size);
+		if (has_type < 0)
+			die(_("cannot read existing object info %s"), oid_to_hex(oid));
+		if (has_type != type || has_size != size)
+			die(_("SHA1 COLLISION FOUND WITH %s !"), oid_to_hex(oid));
+		has_data = read_object_file(oid, &has_type, &has_size);
+		read_unlock();
+		if (!data)
+			data = new_data = get_data_from_pack(obj_entry);
+		if (!has_data)
+			die(_("cannot read existing object %s"), oid_to_hex(oid));
+		if (size != has_size || type != has_type ||
+		    memcmp(data, has_data, size) != 0)
+			die(_("SHA1 COLLISION FOUND WITH %s !"), oid_to_hex(oid));
+		free(has_data);
+	}
+
+	if (strict || do_fsck_object) {
+		read_lock();
+		if (type == OBJ_BLOB) {
+			struct blob *blob = lookup_blob(the_repository, oid);
+			if (blob)
+				blob->object.flags |= FLAG_CHECKED;
+			else
+				die(_("invalid blob object %s"), oid_to_hex(oid));
+			if (do_fsck_object &&
+			    fsck_object(&blob->object, (void *)data, size, &fsck_options))
+				die(_("fsck error in packed object"));
+		} else {
+			struct object *obj;
+			int eaten;
+			void *buf = (void *) data;
+
+			assert(data && "data can only be NULL for large _blobs_");
+
+			/*
+			 * we do not need to free the memory here, as the
+			 * buf is deleted by the caller.
+			 */
+			obj = parse_object_buffer(the_repository, oid, type,
+						  size, buf,
+						  &eaten);
+			if (!obj)
+				die(_("invalid %s"), type_name(type));
+			if (do_fsck_object &&
+			    fsck_object(obj, buf, size, &fsck_options))
+				die(_("fsck error in packed object"));
+			if (strict && fsck_walk(obj, NULL, &fsck_options))
+				die(_("Not all child objects of %s are reachable"), oid_to_hex(&obj->oid));
+
+			if (obj->type == OBJ_TREE) {
+				struct tree *item = (struct tree *) obj;
+				item->buffer = NULL;
+				obj->parsed = 0;
+			}
+			if (obj->type == OBJ_COMMIT) {
+				struct commit *commit = (struct commit *) obj;
+				if (detach_commit_buffer(commit, NULL) != data)
+					BUG("parse_object_buffer transmogrified our buffer");
+			}
+			obj->flags |= FLAG_CHECKED;
+		}
+		read_unlock();
+	}
+
+	free(new_data);
+}
+
+/*
+ * This function is part of find_unresolved_deltas(). There are two
+ * walkers going in the opposite ways.
+ *
+ * The first one in find_unresolved_deltas() traverses down from
+ * parent node to children, deflating nodes along the way. However,
+ * memory for deflated nodes is limited by delta_base_cache_limit, so
+ * at some point parent node's deflated content may be freed.
+ *
+ * The second walker is this function, which goes from current node up
+ * to top parent if necessary to deflate the node. In normal
+ * situation, its parent node would be already deflated, so it just
+ * needs to apply delta.
+ *
+ * In the worst case scenario, parent node is no longer deflated because
+ * we're running out of delta_base_cache_limit; we need to re-deflate
+ * parents, possibly up to the top base.
+ *
+ * All deflated objects here are subject to be freed if we exceed
+ * delta_base_cache_limit, just like in find_unresolved_deltas(), we
+ * just need to make sure the last node is not freed.
+ */
+static void *get_base_data(struct base_data *c)
+{
+	if (!c->data) {
+		struct object_entry *obj = c->obj;
+		struct base_data **delta = NULL;
+		int delta_nr = 0, delta_alloc = 0;
+
+		while (is_delta_type(c->obj->type) && !c->data) {
+			ALLOC_GROW(delta, delta_nr + 1, delta_alloc);
+			delta[delta_nr++] = c;
+			c = c->base;
+		}
+		if (!delta_nr) {
+			c->data = get_data_from_pack(obj);
+			c->size = obj->size;
+			get_thread_data()->base_cache_used += c->size;
+			prune_base_data(c);
+		}
+		for (; delta_nr > 0; delta_nr--) {
+			void *base, *raw;
+			c = delta[delta_nr - 1];
+			obj = c->obj;
+			base = get_base_data(c->base);
+			raw = get_data_from_pack(obj);
+			c->data = patch_delta(
+				base, c->base->size,
+				raw, obj->size,
+				&c->size);
+			free(raw);
+			if (!c->data)
+				bad_object(obj->idx.offset, _("failed to apply delta"));
+			get_thread_data()->base_cache_used += c->size;
+			prune_base_data(c);
+		}
+		free(delta);
+	}
+	return c->data;
+}
+
+static void resolve_delta(struct object_entry *delta_obj,
+			  struct base_data *base, struct base_data *result)
+{
+	void *base_data, *delta_data;
+
+	if (show_stat) {
+		int i = delta_obj - objects;
+		int j = base->obj - objects;
+		obj_stat[i].delta_depth = obj_stat[j].delta_depth + 1;
+		deepest_delta_lock();
+		if (deepest_delta < obj_stat[i].delta_depth)
+			deepest_delta = obj_stat[i].delta_depth;
+		deepest_delta_unlock();
+		obj_stat[i].base_object_no = j;
+	}
+	delta_data = get_data_from_pack(delta_obj);
+	base_data = get_base_data(base);
+	result->obj = delta_obj;
+	result->data = patch_delta(base_data, base->size,
+				   delta_data, delta_obj->size, &result->size);
+	free(delta_data);
+	if (!result->data)
+		bad_object(delta_obj->idx.offset, _("failed to apply delta"));
+	hash_object_file(result->data, result->size,
+			 type_name(delta_obj->real_type), &delta_obj->idx.oid);
+	sha1_object(result->data, NULL, result->size, delta_obj->real_type,
+		    &delta_obj->idx.oid);
+	counter_lock();
+	nr_resolved_deltas++;
+	counter_unlock();
+}
+
+/*
+ * Standard boolean compare-and-swap: atomically check whether "*type" is
+ * "want"; if so, swap in "set" and return true. Otherwise, leave it untouched
+ * and return false.
+ */
+static int compare_and_swap_type(signed char *type,
+				 enum object_type want,
+				 enum object_type set)
+{
+	enum object_type old;
+
+	type_cas_lock();
+	old = *type;
+	if (old == want)
+		*type = set;
+	type_cas_unlock();
+
+	return old == want;
+}
+
+static struct base_data *find_unresolved_deltas_1(struct base_data *base,
+						  struct base_data *prev_base)
+{
+	if (base->ref_last == -1 && base->ofs_last == -1) {
+		find_ref_delta_children(&base->obj->idx.oid,
+					&base->ref_first, &base->ref_last,
+					OBJ_REF_DELTA);
+
+		find_ofs_delta_children(base->obj->idx.offset,
+					&base->ofs_first, &base->ofs_last,
+					OBJ_OFS_DELTA);
+
+		if (base->ref_last == -1 && base->ofs_last == -1) {
+			free(base->data);
+			return NULL;
+		}
+
+		link_base_data(prev_base, base);
+	}
+
+	if (base->ref_first <= base->ref_last) {
+		struct object_entry *child = objects + ref_deltas[base->ref_first].obj_no;
+		struct base_data *result = alloc_base_data();
+
+		if (!compare_and_swap_type(&child->real_type, OBJ_REF_DELTA,
+					   base->obj->real_type))
+			BUG("child->real_type != OBJ_REF_DELTA");
+
+		resolve_delta(child, base, result);
+		if (base->ref_first == base->ref_last && base->ofs_last == -1)
+			free_base_data(base);
+
+		base->ref_first++;
+		return result;
+	}
+
+	if (base->ofs_first <= base->ofs_last) {
+		struct object_entry *child = objects + ofs_deltas[base->ofs_first].obj_no;
+		struct base_data *result = alloc_base_data();
+
+		assert(child->real_type == OBJ_OFS_DELTA);
+		child->real_type = base->obj->real_type;
+		resolve_delta(child, base, result);
+		if (base->ofs_first == base->ofs_last)
+			free_base_data(base);
+
+		base->ofs_first++;
+		return result;
+	}
+
+	unlink_base_data(base);
+	return NULL;
+}
+
+static void find_unresolved_deltas(struct base_data *base)
+{
+	struct base_data *new_base, *prev_base = NULL;
+	for (;;) {
+		new_base = find_unresolved_deltas_1(base, prev_base);
+
+		if (new_base) {
+			prev_base = base;
+			base = new_base;
+		} else {
+			free(base);
+			base = prev_base;
+			if (!base)
+				return;
+			prev_base = base->base;
+		}
+	}
+}
+
+static int compare_ofs_delta_entry(const void *a, const void *b)
+{
+	const struct ofs_delta_entry *delta_a = a;
+	const struct ofs_delta_entry *delta_b = b;
+
+	return delta_a->offset < delta_b->offset ? -1 :
+	       delta_a->offset > delta_b->offset ?  1 :
+	       0;
+}
+
+static int compare_ref_delta_entry(const void *a, const void *b)
+{
+	const struct ref_delta_entry *delta_a = a;
+	const struct ref_delta_entry *delta_b = b;
+
+	return oidcmp(&delta_a->oid, &delta_b->oid);
+}
+
+static void resolve_base(struct object_entry *obj)
+{
+	struct base_data *base_obj = alloc_base_data();
+	base_obj->obj = obj;
+	base_obj->data = NULL;
+	find_unresolved_deltas(base_obj);
+}
+
+static void *threaded_second_pass(void *data)
+{
+	set_thread_data(data);
+	for (;;) {
+		int i;
+		counter_lock();
+		display_progress(progress, nr_resolved_deltas);
+		counter_unlock();
+		work_lock();
+		while (nr_dispatched < nr_objects &&
+		       is_delta_type(objects[nr_dispatched].type))
+			nr_dispatched++;
+		if (nr_dispatched >= nr_objects) {
+			work_unlock();
+			break;
+		}
+		i = nr_dispatched++;
+		work_unlock();
+
+		resolve_base(&objects[i]);
+	}
+	return NULL;
+}
+
+/*
+ * First pass:
+ * - find locations of all objects;
+ * - calculate SHA1 of all non-delta objects;
+ * - remember base (SHA1 or offset) for all deltas.
+ */
+static void parse_pack_objects(unsigned char *hash)
+{
+	int i, nr_delays = 0;
+	struct ofs_delta_entry *ofs_delta = ofs_deltas;
+	struct object_id ref_delta_oid;
+	struct stat st;
+
+	if (verbose)
+		progress = start_progress(
+				from_stdin ? _("Receiving objects") : _("Indexing objects"),
+				nr_objects);
+	for (i = 0; i < nr_objects; i++) {
+		struct object_entry *obj = &objects[i];
+		void *data = unpack_raw_entry(obj, &ofs_delta->offset,
+					      &ref_delta_oid,
+					      &obj->idx.oid);
+		obj->real_type = obj->type;
+		if (obj->type == OBJ_OFS_DELTA) {
+			nr_ofs_deltas++;
+			ofs_delta->obj_no = i;
+			ofs_delta++;
+		} else if (obj->type == OBJ_REF_DELTA) {
+			ALLOC_GROW(ref_deltas, nr_ref_deltas + 1, ref_deltas_alloc);
+			oidcpy(&ref_deltas[nr_ref_deltas].oid, &ref_delta_oid);
+			ref_deltas[nr_ref_deltas].obj_no = i;
+			nr_ref_deltas++;
+		} else if (!data) {
+			/* large blobs, check later */
+			obj->real_type = OBJ_BAD;
+			nr_delays++;
+		} else
+			sha1_object(data, NULL, obj->size, obj->type,
+				    &obj->idx.oid);
+		free(data);
+		display_progress(progress, i+1);
+	}
+	objects[i].idx.offset = consumed_bytes;
+	stop_progress(&progress);
+
+	/* Check pack integrity */
+	flush();
+	the_hash_algo->final_fn(hash, &input_ctx);
+	if (!hasheq(fill(the_hash_algo->rawsz), hash))
+		die(_("pack is corrupted (SHA1 mismatch)"));
+	use(the_hash_algo->rawsz);
+
+	/* If input_fd is a file, we should have reached its end now. */
+	if (fstat(input_fd, &st))
+		die_errno(_("cannot fstat packfile"));
+	if (S_ISREG(st.st_mode) &&
+			lseek(input_fd, 0, SEEK_CUR) - input_len != st.st_size)
+		die(_("pack has junk at the end"));
+
+	for (i = 0; i < nr_objects; i++) {
+		struct object_entry *obj = &objects[i];
+		if (obj->real_type != OBJ_BAD)
+			continue;
+		obj->real_type = obj->type;
+		sha1_object(NULL, obj, obj->size, obj->type,
+			    &obj->idx.oid);
+		nr_delays--;
+	}
+	if (nr_delays)
+		die(_("confusion beyond insanity in parse_pack_objects()"));
+}
+
+/*
+ * Second pass:
+ * - for all non-delta objects, look if it is used as a base for
+ *   deltas;
+ * - if used as a base, uncompress the object and apply all deltas,
+ *   recursively checking if the resulting object is used as a base
+ *   for some more deltas.
+ */
+static void resolve_deltas(void)
+{
+	int i;
+
+	if (!nr_ofs_deltas && !nr_ref_deltas)
+		return;
+
+	/* Sort deltas by base SHA1/offset for fast searching */
+	QSORT(ofs_deltas, nr_ofs_deltas, compare_ofs_delta_entry);
+	QSORT(ref_deltas, nr_ref_deltas, compare_ref_delta_entry);
+
+	if (verbose || show_resolving_progress)
+		progress = start_progress(_("Resolving deltas"),
+					  nr_ref_deltas + nr_ofs_deltas);
+
+	nr_dispatched = 0;
+	if (nr_threads > 1 || getenv("GIT_FORCE_THREADS")) {
+		init_thread();
+		for (i = 0; i < nr_threads; i++) {
+			int ret = pthread_create(&thread_data[i].thread, NULL,
+						 threaded_second_pass, thread_data + i);
+			if (ret)
+				die(_("unable to create thread: %s"),
+				    strerror(ret));
+		}
+		for (i = 0; i < nr_threads; i++)
+			pthread_join(thread_data[i].thread, NULL);
+		cleanup_thread();
+		return;
+	}
+
+	for (i = 0; i < nr_objects; i++) {
+		struct object_entry *obj = &objects[i];
+
+		if (is_delta_type(obj->type))
+			continue;
+		resolve_base(obj);
+		display_progress(progress, nr_resolved_deltas);
+	}
+}
+
+/*
+ * Third pass:
+ * - append objects to convert thin pack to full pack if required
+ * - write the final pack hash
+ */
+static void fix_unresolved_deltas(struct hashfile *f);
+static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned char *pack_hash)
+{
+	if (nr_ref_deltas + nr_ofs_deltas == nr_resolved_deltas) {
+		stop_progress(&progress);
+		/* Flush remaining pack final hash. */
+		flush();
+		return;
+	}
+
+	if (fix_thin_pack) {
+		struct hashfile *f;
+		unsigned char read_hash[GIT_MAX_RAWSZ], tail_hash[GIT_MAX_RAWSZ];
+		struct strbuf msg = STRBUF_INIT;
+		int nr_unresolved = nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas;
+		int nr_objects_initial = nr_objects;
+		if (nr_unresolved <= 0)
+			die(_("confusion beyond insanity"));
+		REALLOC_ARRAY(objects, nr_objects + nr_unresolved + 1);
+		memset(objects + nr_objects + 1, 0,
+		       nr_unresolved * sizeof(*objects));
+		f = hashfd(output_fd, curr_pack);
+		fix_unresolved_deltas(f);
+		strbuf_addf(&msg, Q_("completed with %d local object",
+				     "completed with %d local objects",
+				     nr_objects - nr_objects_initial),
+			    nr_objects - nr_objects_initial);
+		stop_progress_msg(&progress, msg.buf);
+		strbuf_release(&msg);
+		finalize_hashfile(f, tail_hash, 0);
+		hashcpy(read_hash, pack_hash);
+		fixup_pack_header_footer(output_fd, pack_hash,
+					 curr_pack, nr_objects,
+					 read_hash, consumed_bytes-the_hash_algo->rawsz);
+		if (!hasheq(read_hash, tail_hash))
+			die(_("Unexpected tail checksum for %s "
+			      "(disk corruption?)"), curr_pack);
+	}
+	if (nr_ofs_deltas + nr_ref_deltas != nr_resolved_deltas)
+		die(Q_("pack has %d unresolved delta",
+		       "pack has %d unresolved deltas",
+		       nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas),
+		    nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas);
+}
+
+static int write_compressed(struct hashfile *f, void *in, unsigned int size)
+{
+	git_zstream stream;
+	int status;
+	unsigned char outbuf[4096];
+
+	git_deflate_init(&stream, zlib_compression_level);
+	stream.next_in = in;
+	stream.avail_in = size;
+
+	do {
+		stream.next_out = outbuf;
+		stream.avail_out = sizeof(outbuf);
+		status = git_deflate(&stream, Z_FINISH);
+		hashwrite(f, outbuf, sizeof(outbuf) - stream.avail_out);
+	} while (status == Z_OK);
+
+	if (status != Z_STREAM_END)
+		die(_("unable to deflate appended object (%d)"), status);
+	size = stream.total_out;
+	git_deflate_end(&stream);
+	return size;
+}
+
+static struct object_entry *append_obj_to_pack(struct hashfile *f,
+			       const unsigned char *sha1, void *buf,
+			       unsigned long size, enum object_type type)
+{
+	struct object_entry *obj = &objects[nr_objects++];
+	unsigned char header[10];
+	unsigned long s = size;
+	int n = 0;
+	unsigned char c = (type << 4) | (s & 15);
+	s >>= 4;
+	while (s) {
+		header[n++] = c | 0x80;
+		c = s & 0x7f;
+		s >>= 7;
+	}
+	header[n++] = c;
+	crc32_begin(f);
+	hashwrite(f, header, n);
+	obj[0].size = size;
+	obj[0].hdr_size = n;
+	obj[0].type = type;
+	obj[0].real_type = type;
+	obj[1].idx.offset = obj[0].idx.offset + n;
+	obj[1].idx.offset += write_compressed(f, buf, size);
+	obj[0].idx.crc32 = crc32_end(f);
+	hashflush(f);
+	hashcpy(obj->idx.oid.hash, sha1);
+	return obj;
+}
+
+static int delta_pos_compare(const void *_a, const void *_b)
+{
+	struct ref_delta_entry *a = *(struct ref_delta_entry **)_a;
+	struct ref_delta_entry *b = *(struct ref_delta_entry **)_b;
+	return a->obj_no - b->obj_no;
+}
+
+static void fix_unresolved_deltas(struct hashfile *f)
+{
+	struct ref_delta_entry **sorted_by_pos;
+	int i;
+
+	/*
+	 * Since many unresolved deltas may well be themselves base objects
+	 * for more unresolved deltas, we really want to include the
+	 * smallest number of base objects that would cover as much delta
+	 * as possible by picking the
+	 * trunc deltas first, allowing for other deltas to resolve without
+	 * additional base objects.  Since most base objects are to be found
+	 * before deltas depending on them, a good heuristic is to start
+	 * resolving deltas in the same order as their position in the pack.
+	 */
+	ALLOC_ARRAY(sorted_by_pos, nr_ref_deltas);
+	for (i = 0; i < nr_ref_deltas; i++)
+		sorted_by_pos[i] = &ref_deltas[i];
+	QSORT(sorted_by_pos, nr_ref_deltas, delta_pos_compare);
+
+	if (repository_format_partial_clone) {
+		/*
+		 * Prefetch the delta bases.
+		 */
+		struct oid_array to_fetch = OID_ARRAY_INIT;
+		for (i = 0; i < nr_ref_deltas; i++) {
+			struct ref_delta_entry *d = sorted_by_pos[i];
+			if (!oid_object_info_extended(the_repository, &d->oid,
+						      NULL,
+						      OBJECT_INFO_FOR_PREFETCH))
+				continue;
+			oid_array_append(&to_fetch, &d->oid);
+		}
+		if (to_fetch.nr)
+			fetch_objects(repository_format_partial_clone,
+				      to_fetch.oid, to_fetch.nr);
+		oid_array_clear(&to_fetch);
+	}
+
+	for (i = 0; i < nr_ref_deltas; i++) {
+		struct ref_delta_entry *d = sorted_by_pos[i];
+		enum object_type type;
+		struct base_data *base_obj = alloc_base_data();
+
+		if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
+			continue;
+		base_obj->data = read_object_file(&d->oid, &type,
+						  &base_obj->size);
+		if (!base_obj->data)
+			continue;
+
+		if (check_object_signature(&d->oid, base_obj->data,
+				base_obj->size, type_name(type)))
+			die(_("local object %s is corrupt"), oid_to_hex(&d->oid));
+		base_obj->obj = append_obj_to_pack(f, d->oid.hash,
+					base_obj->data, base_obj->size, type);
+		find_unresolved_deltas(base_obj);
+		display_progress(progress, nr_resolved_deltas);
+	}
+	free(sorted_by_pos);
+}
+
+static const char *derive_filename(const char *pack_name, const char *suffix,
+				   struct strbuf *buf)
+{
+	size_t len;
+	if (!strip_suffix(pack_name, ".pack", &len))
+		die(_("packfile name '%s' does not end with '.pack'"),
+		    pack_name);
+	strbuf_add(buf, pack_name, len);
+	strbuf_addch(buf, '.');
+	strbuf_addstr(buf, suffix);
+	return buf->buf;
+}
+
+static void write_special_file(const char *suffix, const char *msg,
+			       const char *pack_name, const unsigned char *hash,
+			       const char **report)
+{
+	struct strbuf name_buf = STRBUF_INIT;
+	const char *filename;
+	int fd;
+	int msg_len = strlen(msg);
+
+	if (pack_name)
+		filename = derive_filename(pack_name, suffix, &name_buf);
+	else
+		filename = odb_pack_name(&name_buf, hash, suffix);
+
+	fd = odb_pack_keep(filename);
+	if (fd < 0) {
+		if (errno != EEXIST)
+			die_errno(_("cannot write %s file '%s'"),
+				  suffix, filename);
+	} else {
+		if (msg_len > 0) {
+			write_or_die(fd, msg, msg_len);
+			write_or_die(fd, "\n", 1);
+		}
+		if (close(fd) != 0)
+			die_errno(_("cannot close written %s file '%s'"),
+				  suffix, filename);
+		if (report)
+			*report = suffix;
+	}
+	strbuf_release(&name_buf);
+}
+
+static void final(const char *final_pack_name, const char *curr_pack_name,
+		  const char *final_index_name, const char *curr_index_name,
+		  const char *keep_msg, const char *promisor_msg,
+		  unsigned char *hash)
+{
+	const char *report = "pack";
+	struct strbuf pack_name = STRBUF_INIT;
+	struct strbuf index_name = STRBUF_INIT;
+	int err;
+
+	if (!from_stdin) {
+		close(input_fd);
+	} else {
+		fsync_or_die(output_fd, curr_pack_name);
+		err = close(output_fd);
+		if (err)
+			die_errno(_("error while closing pack file"));
+	}
+
+	if (keep_msg)
+		write_special_file("keep", keep_msg, final_pack_name, hash,
+				   &report);
+	if (promisor_msg)
+		write_special_file("promisor", promisor_msg, final_pack_name,
+				   hash, NULL);
+
+	if (final_pack_name != curr_pack_name) {
+		if (!final_pack_name)
+			final_pack_name = odb_pack_name(&pack_name, hash, "pack");
+		if (finalize_object_file(curr_pack_name, final_pack_name))
+			die(_("cannot store pack file"));
+	} else if (from_stdin)
+		chmod(final_pack_name, 0444);
+
+	if (final_index_name != curr_index_name) {
+		if (!final_index_name)
+			final_index_name = odb_pack_name(&index_name, hash, "idx");
+		if (finalize_object_file(curr_index_name, final_index_name))
+			die(_("cannot store index file"));
+	} else
+		chmod(final_index_name, 0444);
+
+	if (do_fsck_object) {
+		struct packed_git *p;
+		p = add_packed_git(final_index_name, strlen(final_index_name), 0);
+		if (p)
+			install_packed_git(the_repository, p);
+	}
+
+	if (!from_stdin) {
+		printf("%s\n", sha1_to_hex(hash));
+	} else {
+		struct strbuf buf = STRBUF_INIT;
+
+		strbuf_addf(&buf, "%s\t%s\n", report, sha1_to_hex(hash));
+		write_or_die(1, buf.buf, buf.len);
+		strbuf_release(&buf);
+
+		/*
+		 * Let's just mimic git-unpack-objects here and write
+		 * the last part of the input buffer to stdout.
+		 */
+		while (input_len) {
+			err = xwrite(1, input_buffer + input_offset, input_len);
+			if (err <= 0)
+				break;
+			input_len -= err;
+			input_offset += err;
+		}
+	}
+
+	strbuf_release(&index_name);
+	strbuf_release(&pack_name);
+}
+
+static int git_index_pack_config(const char *k, const char *v, void *cb)
+{
+	struct pack_idx_option *opts = cb;
+
+	if (!strcmp(k, "pack.indexversion")) {
+		opts->version = git_config_int(k, v);
+		if (opts->version > 2)
+			die(_("bad pack.indexversion=%"PRIu32), opts->version);
+		return 0;
+	}
+	if (!strcmp(k, "pack.threads")) {
+		nr_threads = git_config_int(k, v);
+		if (nr_threads < 0)
+			die(_("invalid number of threads specified (%d)"),
+			    nr_threads);
+		if (!HAVE_THREADS && nr_threads != 1) {
+			warning(_("no threads support, ignoring %s"), k);
+			nr_threads = 1;
+		}
+		return 0;
+	}
+	return git_default_config(k, v, cb);
+}
+
+static int cmp_uint32(const void *a_, const void *b_)
+{
+	uint32_t a = *((uint32_t *)a_);
+	uint32_t b = *((uint32_t *)b_);
+
+	return (a < b) ? -1 : (a != b);
+}
+
+static void read_v2_anomalous_offsets(struct packed_git *p,
+				      struct pack_idx_option *opts)
+{
+	const uint32_t *idx1, *idx2;
+	uint32_t i;
+	const uint32_t hashwords = the_hash_algo->rawsz / sizeof(uint32_t);
+
+	/* The address of the 4-byte offset table */
+	idx1 = (((const uint32_t *)p->index_data)
+		+ 2 /* 8-byte header */
+		+ 256 /* fan out */
+		+ hashwords * p->num_objects /* object ID table */
+		+ p->num_objects /* CRC32 table */
+		);
+
+	/* The address of the 8-byte offset table */
+	idx2 = idx1 + p->num_objects;
+
+	for (i = 0; i < p->num_objects; i++) {
+		uint32_t off = ntohl(idx1[i]);
+		if (!(off & 0x80000000))
+			continue;
+		off = off & 0x7fffffff;
+		check_pack_index_ptr(p, &idx2[off * 2]);
+		if (idx2[off * 2])
+			continue;
+		/*
+		 * The real offset is ntohl(idx2[off * 2]) in high 4
+		 * octets, and ntohl(idx2[off * 2 + 1]) in low 4
+		 * octets.  But idx2[off * 2] is Zero!!!
+		 */
+		ALLOC_GROW(opts->anomaly, opts->anomaly_nr + 1, opts->anomaly_alloc);
+		opts->anomaly[opts->anomaly_nr++] = ntohl(idx2[off * 2 + 1]);
+	}
+
+	QSORT(opts->anomaly, opts->anomaly_nr, cmp_uint32);
+}
+
+static void read_idx_option(struct pack_idx_option *opts, const char *pack_name)
+{
+	struct packed_git *p = add_packed_git(pack_name, strlen(pack_name), 1);
+
+	if (!p)
+		die(_("Cannot open existing pack file '%s'"), pack_name);
+	if (open_pack_index(p))
+		die(_("Cannot open existing pack idx file for '%s'"), pack_name);
+
+	/* Read the attributes from the existing idx file */
+	opts->version = p->index_version;
+
+	if (opts->version == 2)
+		read_v2_anomalous_offsets(p, opts);
+
+	/*
+	 * Get rid of the idx file as we do not need it anymore.
+	 * NEEDSWORK: extract this bit from free_pack_by_name() in
+	 * sha1-file.c, perhaps?  It shouldn't matter very much as we
+	 * know we haven't installed this pack (hence we never have
+	 * read anything from it).
+	 */
+	close_pack_index(p);
+	free(p);
+}
+
+static void show_pack_info(int stat_only)
+{
+	int i, baseobjects = nr_objects - nr_ref_deltas - nr_ofs_deltas;
+	unsigned long *chain_histogram = NULL;
+
+	if (deepest_delta)
+		chain_histogram = xcalloc(deepest_delta, sizeof(unsigned long));
+
+	for (i = 0; i < nr_objects; i++) {
+		struct object_entry *obj = &objects[i];
+
+		if (is_delta_type(obj->type))
+			chain_histogram[obj_stat[i].delta_depth - 1]++;
+		if (stat_only)
+			continue;
+		printf("%s %-6s %"PRIuMAX" %"PRIuMAX" %"PRIuMAX,
+		       oid_to_hex(&obj->idx.oid),
+		       type_name(obj->real_type), (uintmax_t)obj->size,
+		       (uintmax_t)(obj[1].idx.offset - obj->idx.offset),
+		       (uintmax_t)obj->idx.offset);
+		if (is_delta_type(obj->type)) {
+			struct object_entry *bobj = &objects[obj_stat[i].base_object_no];
+			printf(" %u %s", obj_stat[i].delta_depth,
+			       oid_to_hex(&bobj->idx.oid));
+		}
+		putchar('\n');
+	}
+
+	if (baseobjects)
+		printf_ln(Q_("non delta: %d object",
+			     "non delta: %d objects",
+			     baseobjects),
+			  baseobjects);
+	for (i = 0; i < deepest_delta; i++) {
+		if (!chain_histogram[i])
+			continue;
+		printf_ln(Q_("chain length = %d: %lu object",
+			     "chain length = %d: %lu objects",
+			     chain_histogram[i]),
+			  i + 1,
+			  chain_histogram[i]);
+	}
+}
+
+int cmd_index_pack(int argc, const char **argv, const char *prefix)
+{
+	int i, fix_thin_pack = 0, verify = 0, stat_only = 0;
+	const char *curr_index;
+	const char *index_name = NULL, *pack_name = NULL;
+	const char *keep_msg = NULL;
+	const char *promisor_msg = NULL;
+	struct strbuf index_name_buf = STRBUF_INIT;
+	struct pack_idx_entry **idx_objects;
+	struct pack_idx_option opts;
+	unsigned char pack_hash[GIT_MAX_RAWSZ];
+	unsigned foreign_nr = 1;	/* zero is a "good" value, assume bad */
+	int report_end_of_input = 0;
+
+	/*
+	 * index-pack never needs to fetch missing objects except when
+	 * REF_DELTA bases are missing (which are explicitly handled). It only
+	 * accesses the repo to do hash collision checks and to check which
+	 * REF_DELTA bases need to be fetched.
+	 */
+	fetch_if_missing = 0;
+
+	if (argc == 2 && !strcmp(argv[1], "-h"))
+		usage(index_pack_usage);
+
+	read_replace_refs = 0;
+	fsck_options.walk = mark_link;
+
+	reset_pack_idx_option(&opts);
+	git_config(git_index_pack_config, &opts);
+	if (prefix && chdir(prefix))
+		die(_("Cannot come back to cwd"));
+
+	for (i = 1; i < argc; i++) {
+		const char *arg = argv[i];
+
+		if (*arg == '-') {
+			if (!strcmp(arg, "--stdin")) {
+				from_stdin = 1;
+			} else if (!strcmp(arg, "--fix-thin")) {
+				fix_thin_pack = 1;
+			} else if (skip_to_optional_arg(arg, "--strict", &arg)) {
+				strict = 1;
+				do_fsck_object = 1;
+				fsck_set_msg_types(&fsck_options, arg);
+			} else if (!strcmp(arg, "--check-self-contained-and-connected")) {
+				strict = 1;
+				check_self_contained_and_connected = 1;
+			} else if (!strcmp(arg, "--fsck-objects")) {
+				do_fsck_object = 1;
+			} else if (!strcmp(arg, "--verify")) {
+				verify = 1;
+			} else if (!strcmp(arg, "--verify-stat")) {
+				verify = 1;
+				show_stat = 1;
+			} else if (!strcmp(arg, "--verify-stat-only")) {
+				verify = 1;
+				show_stat = 1;
+				stat_only = 1;
+			} else if (skip_to_optional_arg(arg, "--keep", &keep_msg)) {
+				; /* nothing to do */
+			} else if (skip_to_optional_arg(arg, "--promisor", &promisor_msg)) {
+				; /* already parsed */
+			} else if (starts_with(arg, "--threads=")) {
+				char *end;
+				nr_threads = strtoul(arg+10, &end, 0);
+				if (!arg[10] || *end || nr_threads < 0)
+					usage(index_pack_usage);
+				if (!HAVE_THREADS && nr_threads != 1) {
+					warning(_("no threads support, ignoring %s"), arg);
+					nr_threads = 1;
+				}
+			} else if (starts_with(arg, "--pack_header=")) {
+				struct pack_header *hdr;
+				char *c;
+
+				hdr = (struct pack_header *)input_buffer;
+				hdr->hdr_signature = htonl(PACK_SIGNATURE);
+				hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));
+				if (*c != ',')
+					die(_("bad %s"), arg);
+				hdr->hdr_entries = htonl(strtoul(c + 1, &c, 10));
+				if (*c)
+					die(_("bad %s"), arg);
+				input_len = sizeof(*hdr);
+			} else if (!strcmp(arg, "-v")) {
+				verbose = 1;
+			} else if (!strcmp(arg, "--show-resolving-progress")) {
+				show_resolving_progress = 1;
+			} else if (!strcmp(arg, "--report-end-of-input")) {
+				report_end_of_input = 1;
+			} else if (!strcmp(arg, "-o")) {
+				if (index_name || (i+1) >= argc)
+					usage(index_pack_usage);
+				index_name = argv[++i];
+			} else if (starts_with(arg, "--index-version=")) {
+				char *c;
+				opts.version = strtoul(arg + 16, &c, 10);
+				if (opts.version > 2)
+					die(_("bad %s"), arg);
+				if (*c == ',')
+					opts.off32_limit = strtoul(c+1, &c, 0);
+				if (*c || opts.off32_limit & 0x80000000)
+					die(_("bad %s"), arg);
+			} else if (skip_prefix(arg, "--max-input-size=", &arg)) {
+				max_input_size = strtoumax(arg, NULL, 10);
+			} else
+				usage(index_pack_usage);
+			continue;
+		}
+
+		if (pack_name)
+			usage(index_pack_usage);
+		pack_name = arg;
+	}
+
+	if (!pack_name && !from_stdin)
+		usage(index_pack_usage);
+	if (fix_thin_pack && !from_stdin)
+		die(_("--fix-thin cannot be used without --stdin"));
+	if (from_stdin && !startup_info->have_repository)
+		die(_("--stdin requires a git repository"));
+	if (!index_name && pack_name)
+		index_name = derive_filename(pack_name, "idx", &index_name_buf);
+
+	if (verify) {
+		if (!index_name)
+			die(_("--verify with no packfile name given"));
+		read_idx_option(&opts, index_name);
+		opts.flags |= WRITE_IDX_VERIFY | WRITE_IDX_STRICT;
+	}
+	if (strict)
+		opts.flags |= WRITE_IDX_STRICT;
+
+	if (HAVE_THREADS && !nr_threads) {
+		nr_threads = online_cpus();
+		/* An experiment showed that more threads does not mean faster */
+		if (nr_threads > 3)
+			nr_threads = 3;
+	}
+
+	curr_pack = open_pack_file(pack_name);
+	parse_pack_header();
+	objects = xcalloc(st_add(nr_objects, 1), sizeof(struct object_entry));
+	if (show_stat)
+		obj_stat = xcalloc(st_add(nr_objects, 1), sizeof(struct object_stat));
+	ofs_deltas = xcalloc(nr_objects, sizeof(struct ofs_delta_entry));
+	parse_pack_objects(pack_hash);
+	if (report_end_of_input)
+		write_in_full(2, "\0", 1);
+	resolve_deltas();
+	conclude_pack(fix_thin_pack, curr_pack, pack_hash);
+	free(ofs_deltas);
+	free(ref_deltas);
+	if (strict)
+		foreign_nr = check_objects();
+
+	if (show_stat)
+		show_pack_info(stat_only);
+
+	ALLOC_ARRAY(idx_objects, nr_objects);
+	for (i = 0; i < nr_objects; i++)
+		idx_objects[i] = &objects[i].idx;
+	curr_index = write_idx_file(index_name, idx_objects, nr_objects, &opts, pack_hash);
+	free(idx_objects);
+
+	if (!verify)
+		final(pack_name, curr_pack,
+		      index_name, curr_index,
+		      keep_msg, promisor_msg,
+		      pack_hash);
+	else
+		close(input_fd);
+
+	if (do_fsck_object && fsck_finish(&fsck_options))
+		die(_("fsck error in pack objects"));
+
+	free(objects);
+	strbuf_release(&index_name_buf);
+	if (pack_name == NULL)
+		free((void *) curr_pack);
+	if (index_name == NULL)
+		free((void *) curr_index);
+
+	/*
+	 * Let the caller know this pack is not self contained
+	 */
+	if (check_self_contained_and_connected && foreign_nr)
+		return 1;
+
+	return 0;
+}