git/fetch-pack.c

#include "cache.h"
#include "repository.h"
#include "config.h"
#include "lockfile.h"
#include "refs.h"
#include "pkt-line.h"
#include "commit.h"
#include "tag.h"
#include "exec_cmd.h"
#include "pack.h"
#include "sideband.h"
#include "fetch-pack.h"
#include "remote.h"
#include "run-command.h"
#include "connect.h"
#include "transport.h"
#include "version.h"
#include "prio-queue.h"
#include "sha1-array.h"
#include "oidset.h"
#include "packfile.h"
#include "object-store.h"

static int transfer_unpack_limit = -1;
static int fetch_unpack_limit = -1;
static int unpack_limit = 100;
static int prefer_ofs_delta = 1;
static int no_done;
static int deepen_since_ok;
static int deepen_not_ok;
static int fetch_fsck_objects = -1;
static int transfer_fsck_objects = -1;
static int agent_supported;
static int server_supports_filtering;
static struct lock_file shallow_lock;
static const char *alternate_shallow_file;

/* Remember to update object flag allocation in object.h */
#define COMPLETE	(1U << 0)
#define COMMON		(1U << 1)
#define COMMON_REF	(1U << 2)
#define SEEN		(1U << 3)
#define POPPED		(1U << 4)
#define ALTERNATE	(1U << 5)

static int marked;

/*
 * After sending this many "have"s if we do not get any new ACK , we
 * give up traversing our history.
 */
#define MAX_IN_VAIN 256

static struct prio_queue rev_list = { compare_commits_by_commit_date };
static int non_common_revs, multi_ack, use_sideband;
/* Allow specifying sha1 if it is a ref tip. */
#define ALLOW_TIP_SHA1	01
/* Allow request of a sha1 if it is reachable from a ref (possibly hidden ref). */
#define ALLOW_REACHABLE_SHA1	02
static unsigned int allow_unadvertised_object_request;

__attribute__((format (printf, 2, 3)))
static inline void print_verbose(const struct fetch_pack_args *args,
				 const char *fmt, ...)
{
	va_list params;

	if (!args->verbose)
		return;

	va_start(params, fmt);
	vfprintf(stderr, fmt, params);
	va_end(params);
	fputc('\n', stderr);
}

struct alternate_object_cache {
	struct object **items;
	size_t nr, alloc;
};

static void cache_one_alternate(const char *refname,
				const struct object_id *oid,
				void *vcache)
{
	struct alternate_object_cache *cache = vcache;
	struct object *obj = parse_object(oid);

	if (!obj || (obj->flags & ALTERNATE))
		return;

	obj->flags |= ALTERNATE;
	ALLOC_GROW(cache->items, cache->nr + 1, cache->alloc);
	cache->items[cache->nr++] = obj;
}

static void for_each_cached_alternate(void (*cb)(struct object *))
{
	static int initialized;
	static struct alternate_object_cache cache;
	size_t i;

	if (!initialized) {
		for_each_alternate_ref(cache_one_alternate, &cache);
		initialized = 1;
	}

	for (i = 0; i < cache.nr; i++)
		cb(cache.items[i]);
}

static void rev_list_push(struct commit *commit, int mark)
{
	if (!(commit->object.flags & mark)) {
		commit->object.flags |= mark;

		if (parse_commit(commit))
			return;

		prio_queue_put(&rev_list, commit);

		if (!(commit->object.flags & COMMON))
			non_common_revs++;
	}
}

static int rev_list_insert_ref(const char *refname, const struct object_id *oid)
{
	struct object *o = deref_tag(parse_object(oid), refname, 0);

	if (o && o->type == OBJ_COMMIT)
		rev_list_push((struct commit *)o, SEEN);

	return 0;
}

static int rev_list_insert_ref_oid(const char *refname, const struct object_id *oid,
				   int flag, void *cb_data)
{
	return rev_list_insert_ref(refname, oid);
}

static int clear_marks(const char *refname, const struct object_id *oid,
		       int flag, void *cb_data)
{
	struct object *o = deref_tag(parse_object(oid), refname, 0);

	if (o && o->type == OBJ_COMMIT)
		clear_commit_marks((struct commit *)o,
				   COMMON | COMMON_REF | SEEN | POPPED);
	return 0;
}

/*
   This function marks a rev and its ancestors as common.
   In some cases, it is desirable to mark only the ancestors (for example
   when only the server does not yet know that they are common).
*/

static void mark_common(struct commit *commit,
		int ancestors_only, int dont_parse)
{
	if (commit != NULL && !(commit->object.flags & COMMON)) {
		struct object *o = (struct object *)commit;

		if (!ancestors_only)
			o->flags |= COMMON;

		if (!(o->flags & SEEN))
			rev_list_push(commit, SEEN);
		else {
			struct commit_list *parents;

			if (!ancestors_only && !(o->flags & POPPED))
				non_common_revs--;
			if (!o->parsed && !dont_parse)
				if (parse_commit(commit))
					return;

			for (parents = commit->parents;
					parents;
					parents = parents->next)
				mark_common(parents->item, 0, dont_parse);
		}
	}
}

/*
  Get the next rev to send, ignoring the common.
*/

static const struct object_id *get_rev(void)
{
	struct commit *commit = NULL;

	while (commit == NULL) {
		unsigned int mark;
		struct commit_list *parents;

		if (rev_list.nr == 0 || non_common_revs == 0)
			return NULL;

		commit = prio_queue_get(&rev_list);
		parse_commit(commit);
		parents = commit->parents;

		commit->object.flags |= POPPED;
		if (!(commit->object.flags & COMMON))
			non_common_revs--;

		if (commit->object.flags & COMMON) {
			/* do not send "have", and ignore ancestors */
			commit = NULL;
			mark = COMMON | SEEN;
		} else if (commit->object.flags & COMMON_REF)
			/* send "have", and ignore ancestors */
			mark = COMMON | SEEN;
		else
			/* send "have", also for its ancestors */
			mark = SEEN;

		while (parents) {
			if (!(parents->item->object.flags & SEEN))
				rev_list_push(parents->item, mark);
			if (mark & COMMON)
				mark_common(parents->item, 1, 0);
			parents = parents->next;
		}
	}

	return &commit->object.oid;
}

enum ack_type {
	NAK = 0,
	ACK,
	ACK_continue,
	ACK_common,
	ACK_ready
};

static void consume_shallow_list(struct fetch_pack_args *args, int fd)
{
	if (args->stateless_rpc && args->deepen) {
		/* If we sent a depth we will get back "duplicate"
		 * shallow and unshallow commands every time there
		 * is a block of have lines exchanged.
		 */
		char *line;
		while ((line = packet_read_line(fd, NULL))) {
			if (starts_with(line, "shallow "))
				continue;
			if (starts_with(line, "unshallow "))
				continue;
			die(_("git fetch-pack: expected shallow list"));
		}
	}
}

static enum ack_type get_ack(int fd, struct object_id *result_oid)
{
	int len;
	char *line = packet_read_line(fd, &len);
	const char *arg;

	if (!line)
		die(_("git fetch-pack: expected ACK/NAK, got a flush packet"));
	if (!strcmp(line, "NAK"))
		return NAK;
	if (skip_prefix(line, "ACK ", &arg)) {
		if (!get_oid_hex(arg, result_oid)) {
			arg += 40;
			len -= arg - line;
			if (len < 1)
				return ACK;
			if (strstr(arg, "continue"))
				return ACK_continue;
			if (strstr(arg, "common"))
				return ACK_common;
			if (strstr(arg, "ready"))
				return ACK_ready;
			return ACK;
		}
	}
	if (skip_prefix(line, "ERR ", &arg))
		die(_("remote error: %s"), arg);
	die(_("git fetch-pack: expected ACK/NAK, got '%s'"), line);
}

static void send_request(struct fetch_pack_args *args,
			 int fd, struct strbuf *buf)
{
	if (args->stateless_rpc) {
		send_sideband(fd, -1, buf->buf, buf->len, LARGE_PACKET_MAX);
		packet_flush(fd);
	} else
		write_or_die(fd, buf->buf, buf->len);
}

static void insert_one_alternate_object(struct object *obj)
{
	rev_list_insert_ref(NULL, &obj->oid);
}

#define INITIAL_FLUSH 16
#define PIPESAFE_FLUSH 32
#define LARGE_FLUSH 16384

static int next_flush(struct fetch_pack_args *args, int count)
{
	if (args->stateless_rpc) {
		if (count < LARGE_FLUSH)
			count <<= 1;
		else
			count = count * 11 / 10;
	} else {
		if (count < PIPESAFE_FLUSH)
			count <<= 1;
		else
			count += PIPESAFE_FLUSH;
	}
	return count;
}

static int find_common(struct fetch_pack_args *args,
		       int fd[2], struct object_id *result_oid,
		       struct ref *refs)
{
	int fetching;
	int count = 0, flushes = 0, flush_at = INITIAL_FLUSH, retval;
	const struct object_id *oid;
	unsigned in_vain = 0;
	int got_continue = 0;
	int got_ready = 0;
	struct strbuf req_buf = STRBUF_INIT;
	size_t state_len = 0;

	if (args->stateless_rpc && multi_ack == 1)
		die(_("--stateless-rpc requires multi_ack_detailed"));
	if (marked)
		for_each_ref(clear_marks, NULL);
	marked = 1;

	for_each_ref(rev_list_insert_ref_oid, NULL);
	for_each_cached_alternate(insert_one_alternate_object);

	fetching = 0;
	for ( ; refs ; refs = refs->next) {
		struct object_id *remote = &refs->old_oid;
		const char *remote_hex;
		struct object *o;

		/*
		 * If that object is complete (i.e. it is an ancestor of a
		 * local ref), we tell them we have it but do not have to
		 * tell them about its ancestors, which they already know
		 * about.
		 *
		 * We use lookup_object here because we are only
		 * interested in the case we *know* the object is
		 * reachable and we have already scanned it.
		 */
		if (((o = lookup_object(remote->hash)) != NULL) &&
				(o->flags & COMPLETE)) {
			continue;
		}

		remote_hex = oid_to_hex(remote);
		if (!fetching) {
			struct strbuf c = STRBUF_INIT;
			if (multi_ack == 2)     strbuf_addstr(&c, " multi_ack_detailed");
			if (multi_ack == 1)     strbuf_addstr(&c, " multi_ack");
			if (no_done)            strbuf_addstr(&c, " no-done");
			if (use_sideband == 2)  strbuf_addstr(&c, " side-band-64k");
			if (use_sideband == 1)  strbuf_addstr(&c, " side-band");
			if (args->deepen_relative) strbuf_addstr(&c, " deepen-relative");
			if (args->use_thin_pack) strbuf_addstr(&c, " thin-pack");
			if (args->no_progress)   strbuf_addstr(&c, " no-progress");
			if (args->include_tag)   strbuf_addstr(&c, " include-tag");
			if (prefer_ofs_delta)   strbuf_addstr(&c, " ofs-delta");
			if (deepen_since_ok)    strbuf_addstr(&c, " deepen-since");
			if (deepen_not_ok)      strbuf_addstr(&c, " deepen-not");
			if (agent_supported)    strbuf_addf(&c, " agent=%s",
							    git_user_agent_sanitized());
			if (args->filter_options.choice)
				strbuf_addstr(&c, " filter");
			packet_buf_write(&req_buf, "want %s%s\n", remote_hex, c.buf);
			strbuf_release(&c);
		} else
			packet_buf_write(&req_buf, "want %s\n", remote_hex);
		fetching++;
	}

	if (!fetching) {
		strbuf_release(&req_buf);
		packet_flush(fd[1]);
		return 1;
	}

	if (is_repository_shallow(the_repository))
		write_shallow_commits(&req_buf, 1, NULL);
	if (args->depth > 0)
		packet_buf_write(&req_buf, "deepen %d", args->depth);
	if (args->deepen_since) {
		timestamp_t max_age = approxidate(args->deepen_since);
		packet_buf_write(&req_buf, "deepen-since %"PRItime, max_age);
	}
	if (args->deepen_not) {
		int i;
		for (i = 0; i < args->deepen_not->nr; i++) {
			struct string_list_item *s = args->deepen_not->items + i;
			packet_buf_write(&req_buf, "deepen-not %s", s->string);
		}
	}
	if (server_supports_filtering && args->filter_options.choice)
		packet_buf_write(&req_buf, "filter %s",
				 args->filter_options.filter_spec);
	packet_buf_flush(&req_buf);
	state_len = req_buf.len;

	if (args->deepen) {
		char *line;
		const char *arg;
		struct object_id oid;

		send_request(args, fd[1], &req_buf);
		while ((line = packet_read_line(fd[0], NULL))) {
			if (skip_prefix(line, "shallow ", &arg)) {
				if (get_oid_hex(arg, &oid))
					die(_("invalid shallow line: %s"), line);
				register_shallow(the_repository, &oid);
				continue;
			}
			if (skip_prefix(line, "unshallow ", &arg)) {
				if (get_oid_hex(arg, &oid))
					die(_("invalid unshallow line: %s"), line);
				if (!lookup_object(oid.hash))
					die(_("object not found: %s"), line);
				/* make sure that it is parsed as shallow */
				if (!parse_object(&oid))
					die(_("error in object: %s"), line);
				if (unregister_shallow(&oid))
					die(_("no shallow found: %s"), line);
				continue;
			}
			die(_("expected shallow/unshallow, got %s"), line);
		}
	} else if (!args->stateless_rpc)
		send_request(args, fd[1], &req_buf);

	if (!args->stateless_rpc) {
		/* If we aren't using the stateless-rpc interface
		 * we don't need to retain the headers.
		 */
		strbuf_setlen(&req_buf, 0);
		state_len = 0;
	}

	flushes = 0;
	retval = -1;
	if (args->no_dependents)
		goto done;
	while ((oid = get_rev())) {
		packet_buf_write(&req_buf, "have %s\n", oid_to_hex(oid));
		print_verbose(args, "have %s", oid_to_hex(oid));
		in_vain++;
		if (flush_at <= ++count) {
			int ack;

			packet_buf_flush(&req_buf);
			send_request(args, fd[1], &req_buf);
			strbuf_setlen(&req_buf, state_len);
			flushes++;
			flush_at = next_flush(args, count);

			/*
			 * We keep one window "ahead" of the other side, and
			 * will wait for an ACK only on the next one
			 */
			if (!args->stateless_rpc && count == INITIAL_FLUSH)
				continue;

			consume_shallow_list(args, fd[0]);
			do {
				ack = get_ack(fd[0], result_oid);
				if (ack)
					print_verbose(args, _("got %s %d %s"), "ack",
						      ack, oid_to_hex(result_oid));
				switch (ack) {
				case ACK:
					flushes = 0;
					multi_ack = 0;
					retval = 0;
					goto done;
				case ACK_common:
				case ACK_ready:
				case ACK_continue: {
					struct commit *commit =
						lookup_commit(result_oid);
					if (!commit)
						die(_("invalid commit %s"), oid_to_hex(result_oid));
					if (args->stateless_rpc
					 && ack == ACK_common
					 && !(commit->object.flags & COMMON)) {
						/* We need to replay the have for this object
						 * on the next RPC request so the peer knows
						 * it is in common with us.
						 */
						const char *hex = oid_to_hex(result_oid);
						packet_buf_write(&req_buf, "have %s\n", hex);
						state_len = req_buf.len;
						/*
						 * Reset in_vain because an ack
						 * for this commit has not been
						 * seen.
						 */
						in_vain = 0;
					} else if (!args->stateless_rpc
						   || ack != ACK_common)
						in_vain = 0;
					mark_common(commit, 0, 1);
					retval = 0;
					got_continue = 1;
					if (ack == ACK_ready) {
						clear_prio_queue(&rev_list);
						got_ready = 1;
					}
					break;
					}
				}
			} while (ack);
			flushes--;
			if (got_continue && MAX_IN_VAIN < in_vain) {
				print_verbose(args, _("giving up"));
				break; /* give up */
			}
		}
	}
done:
	if (!got_ready || !no_done) {
		packet_buf_write(&req_buf, "done\n");
		send_request(args, fd[1], &req_buf);
	}
	print_verbose(args, _("done"));
	if (retval != 0) {
		multi_ack = 0;
		flushes++;
	}
	strbuf_release(&req_buf);

	if (!got_ready || !no_done)
		consume_shallow_list(args, fd[0]);
	while (flushes || multi_ack) {
		int ack = get_ack(fd[0], result_oid);
		if (ack) {
			print_verbose(args, _("got %s (%d) %s"), "ack",
				      ack, oid_to_hex(result_oid));
			if (ack == ACK)
				return 0;
			multi_ack = 1;
			continue;
		}
		flushes--;
	}
	/* it is no error to fetch into a completely empty repo */
	return count ? retval : 0;
}

static struct commit_list *complete;

static int mark_complete(const struct object_id *oid)
{
	struct object *o = parse_object(oid);

	while (o && o->type == OBJ_TAG) {
		struct tag *t = (struct tag *) o;
		if (!t->tagged)
			break; /* broken repository */
		o->flags |= COMPLETE;
		o = parse_object(&t->tagged->oid);
	}
	if (o && o->type == OBJ_COMMIT) {
		struct commit *commit = (struct commit *)o;
		if (!(commit->object.flags & COMPLETE)) {
			commit->object.flags |= COMPLETE;
			commit_list_insert(commit, &complete);
		}
	}
	return 0;
}

static int mark_complete_oid(const char *refname, const struct object_id *oid,
			     int flag, void *cb_data)
{
	return mark_complete(oid);
}

static void mark_recent_complete_commits(struct fetch_pack_args *args,
					 timestamp_t cutoff)
{
	while (complete && cutoff <= complete->item->date) {
		print_verbose(args, _("Marking %s as complete"),
			      oid_to_hex(&complete->item->object.oid));
		pop_most_recent_commit(&complete, COMPLETE);
	}
}

static void add_refs_to_oidset(struct oidset *oids, struct ref *refs)
{
	for (; refs; refs = refs->next)
		oidset_insert(oids, &refs->old_oid);
}

static int tip_oids_contain(struct oidset *tip_oids,
			    struct ref *unmatched, struct ref *newlist,
			    const struct object_id *id)
{
	/*
	 * Note that this only looks at the ref lists the first time it's
	 * called. This works out in filter_refs() because even though it may
	 * add to "newlist" between calls, the additions will always be for
	 * oids that are already in the set.
	 */
	if (!tip_oids->map.map.tablesize) {
		add_refs_to_oidset(tip_oids, unmatched);
		add_refs_to_oidset(tip_oids, newlist);
	}
	return oidset_contains(tip_oids, id);
}

static void filter_refs(struct fetch_pack_args *args,
			struct ref **refs,
			struct ref **sought, int nr_sought)
{
	struct ref *newlist = NULL;
	struct ref **newtail = &newlist;
	struct ref *unmatched = NULL;
	struct ref *ref, *next;
	struct oidset tip_oids = OIDSET_INIT;
	int i;

	i = 0;
	for (ref = *refs; ref; ref = next) {
		int keep = 0;
		next = ref->next;

		if (starts_with(ref->name, "refs/") &&
		    check_refname_format(ref->name, 0))
			; /* trash */
		else {
			while (i < nr_sought) {
				int cmp = strcmp(ref->name, sought[i]->name);
				if (cmp < 0)
					break; /* definitely do not have it */
				else if (cmp == 0) {
					keep = 1; /* definitely have it */
					sought[i]->match_status = REF_MATCHED;
				}
				i++;
			}
		}

		if (!keep && args->fetch_all &&
		    (!args->deepen || !starts_with(ref->name, "refs/tags/")))
			keep = 1;

		if (keep) {
			*newtail = ref;
			ref->next = NULL;
			newtail = &ref->next;
		} else {
			ref->next = unmatched;
			unmatched = ref;
		}
	}

	/* Append unmatched requests to the list */
	for (i = 0; i < nr_sought; i++) {
		struct object_id oid;
		const char *p;

		ref = sought[i];
		if (ref->match_status != REF_NOT_MATCHED)
			continue;
		if (parse_oid_hex(ref->name, &oid, &p) ||
		    *p != '\0' ||
		    oidcmp(&oid, &ref->old_oid))
			continue;

		if ((allow_unadvertised_object_request &
		     (ALLOW_TIP_SHA1 | ALLOW_REACHABLE_SHA1)) ||
		    tip_oids_contain(&tip_oids, unmatched, newlist,
				     &ref->old_oid)) {
			ref->match_status = REF_MATCHED;
			*newtail = copy_ref(ref);
			newtail = &(*newtail)->next;
		} else {
			ref->match_status = REF_UNADVERTISED_NOT_ALLOWED;
		}
	}

	oidset_clear(&tip_oids);
	for (ref = unmatched; ref; ref = next) {
		next = ref->next;
		free(ref);
	}

	*refs = newlist;
}

static void mark_alternate_complete(struct object *obj)
{
	mark_complete(&obj->oid);
}

struct loose_object_iter {
	struct oidset *loose_object_set;
	struct ref *refs;
};

/*
 *  If the number of refs is not larger than the number of loose objects,
 *  this function stops inserting.
 */
static int add_loose_objects_to_set(const struct object_id *oid,
				    const char *path,
				    void *data)
{
	struct loose_object_iter *iter = data;
	oidset_insert(iter->loose_object_set, oid);
	if (iter->refs == NULL)
		return 1;

	iter->refs = iter->refs->next;
	return 0;
}

static int everything_local(struct fetch_pack_args *args,
			    struct ref **refs,
			    struct ref **sought, int nr_sought)
{
	struct ref *ref;
	int retval;
	int old_save_commit_buffer = save_commit_buffer;
	timestamp_t cutoff = 0;
	struct oidset loose_oid_set = OIDSET_INIT;
	int use_oidset = 0;
	struct loose_object_iter iter = {&loose_oid_set, *refs};

	/* Enumerate all loose objects or know refs are not so many. */
	use_oidset = !for_each_loose_object(add_loose_objects_to_set,
					    &iter, 0);

	save_commit_buffer = 0;

	for (ref = *refs; ref; ref = ref->next) {
		struct object *o;
		unsigned int flags = OBJECT_INFO_QUICK;

		if (use_oidset &&
		    !oidset_contains(&loose_oid_set, &ref->old_oid)) {
			/*
			 * I know this does not exist in the loose form,
			 * so check if it exists in a non-loose form.
			 */
			flags |= OBJECT_INFO_IGNORE_LOOSE;
		}

		if (!has_object_file_with_flags(&ref->old_oid, flags))
			continue;
		o = parse_object(&ref->old_oid);
		if (!o)
			continue;

		/* We already have it -- which may mean that we were
		 * in sync with the other side at some time after
		 * that (it is OK if we guess wrong here).
		 */
		if (o->type == OBJ_COMMIT) {
			struct commit *commit = (struct commit *)o;
			if (!cutoff || cutoff < commit->date)
				cutoff = commit->date;
		}
	}

	oidset_clear(&loose_oid_set);

	if (!args->no_dependents) {
		if (!args->deepen) {
			for_each_ref(mark_complete_oid, NULL);
			for_each_cached_alternate(mark_alternate_complete);
			commit_list_sort_by_date(&complete);
			if (cutoff)
				mark_recent_complete_commits(args, cutoff);
		}

		/*
		 * Mark all complete remote refs as common refs.
		 * Don't mark them common yet; the server has to be told so first.
		 */
		for (ref = *refs; ref; ref = ref->next) {
			struct object *o = deref_tag(lookup_object(ref->old_oid.hash),
						     NULL, 0);

			if (!o || o->type != OBJ_COMMIT || !(o->flags & COMPLETE))
				continue;

			if (!(o->flags & SEEN)) {
				rev_list_push((struct commit *)o, COMMON_REF | SEEN);

				mark_common((struct commit *)o, 1, 1);
			}
		}
	}

	filter_refs(args, refs, sought, nr_sought);

	for (retval = 1, ref = *refs; ref ; ref = ref->next) {
		const struct object_id *remote = &ref->old_oid;
		struct object *o;

		o = lookup_object(remote->hash);
		if (!o || !(o->flags & COMPLETE)) {
			retval = 0;
			print_verbose(args, "want %s (%s)", oid_to_hex(remote),
				      ref->name);
			continue;
		}
		print_verbose(args, _("already have %s (%s)"), oid_to_hex(remote),
			      ref->name);
	}

	save_commit_buffer = old_save_commit_buffer;

	return retval;
}

static int sideband_demux(int in, int out, void *data)
{
	int *xd = data;
	int ret;

	ret = recv_sideband("fetch-pack", xd[0], out);
	close(out);
	return ret;
}

static int get_pack(struct fetch_pack_args *args,
		    int xd[2], char **pack_lockfile)
{
	struct async demux;
	int do_keep = args->keep_pack;
	const char *cmd_name;
	struct pack_header header;
	int pass_header = 0;
	struct child_process cmd = CHILD_PROCESS_INIT;
	int ret;

	memset(&demux, 0, sizeof(demux));
	if (use_sideband) {
		/* xd[] is talking with upload-pack; subprocess reads from
		 * xd[0], spits out band#2 to stderr, and feeds us band#1
		 * through demux->out.
		 */
		demux.proc = sideband_demux;
		demux.data = xd;
		demux.out = -1;
		demux.isolate_sigpipe = 1;
		if (start_async(&demux))
			die(_("fetch-pack: unable to fork off sideband demultiplexer"));
	}
	else
		demux.out = xd[0];

	if (!args->keep_pack && unpack_limit) {

		if (read_pack_header(demux.out, &header))
			die(_("protocol error: bad pack header"));
		pass_header = 1;
		if (ntohl(header.hdr_entries) < unpack_limit)
			do_keep = 0;
		else
			do_keep = 1;
	}

	if (alternate_shallow_file) {
		argv_array_push(&cmd.args, "--shallow-file");
		argv_array_push(&cmd.args, alternate_shallow_file);
	}

	if (do_keep || args->from_promisor) {
		if (pack_lockfile)
			cmd.out = -1;
		cmd_name = "index-pack";
		argv_array_push(&cmd.args, cmd_name);
		argv_array_push(&cmd.args, "--stdin");
		if (!args->quiet && !args->no_progress)
			argv_array_push(&cmd.args, "-v");
		if (args->use_thin_pack)
			argv_array_push(&cmd.args, "--fix-thin");
		if (do_keep && (args->lock_pack || unpack_limit)) {
			char hostname[HOST_NAME_MAX + 1];
			if (xgethostname(hostname, sizeof(hostname)))
				xsnprintf(hostname, sizeof(hostname), "localhost");
			argv_array_pushf(&cmd.args,
					"--keep=fetch-pack %"PRIuMAX " on %s",
					(uintmax_t)getpid(), hostname);
		}
		if (args->check_self_contained_and_connected)
			argv_array_push(&cmd.args, "--check-self-contained-and-connected");
		if (args->from_promisor)
			argv_array_push(&cmd.args, "--promisor");
	}
	else {
		cmd_name = "unpack-objects";
		argv_array_push(&cmd.args, cmd_name);
		if (args->quiet || args->no_progress)
			argv_array_push(&cmd.args, "-q");
		args->check_self_contained_and_connected = 0;
	}

	if (pass_header)
		argv_array_pushf(&cmd.args, "--pack_header=%"PRIu32",%"PRIu32,
				 ntohl(header.hdr_version),
				 ntohl(header.hdr_entries));
	if (fetch_fsck_objects >= 0
	    ? fetch_fsck_objects
	    : transfer_fsck_objects >= 0
	    ? transfer_fsck_objects
	    : 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;
	if (start_command(&cmd))
		die(_("fetch-pack: unable to fork off %s"), cmd_name);
	if (do_keep && pack_lockfile) {
		*pack_lockfile = index_pack_lockfile(cmd.out);
		close(cmd.out);
	}

	if (!use_sideband)
		/* Closed by start_command() */
		xd[0] = -1;

	ret = finish_command(&cmd);
	if (!ret || (args->check_self_contained_and_connected && ret == 1))
		args->self_contained_and_connected =
			args->check_self_contained_and_connected &&
			ret == 0;
	else
		die(_("%s failed"), cmd_name);
	if (use_sideband && finish_async(&demux))
		die(_("error in sideband demultiplexer"));
	return 0;
}

static int cmp_ref_by_name(const void *a_, const void *b_)
{
	const struct ref *a = *((const struct ref **)a_);
	const struct ref *b = *((const struct ref **)b_);
	return strcmp(a->name, b->name);
}

static struct ref *do_fetch_pack(struct fetch_pack_args *args,
				 int fd[2],
				 const struct ref *orig_ref,
				 struct ref **sought, int nr_sought,
				 struct shallow_info *si,
				 char **pack_lockfile)
{
	struct ref *ref = copy_ref_list(orig_ref);
	struct object_id oid;
	const char *agent_feature;
	int agent_len;

	sort_ref_list(&ref, ref_compare_name);
	QSORT(sought, nr_sought, cmp_ref_by_name);

	if ((args->depth > 0 || is_repository_shallow(the_repository)) && !server_supports("shallow"))
		die(_("Server does not support shallow clients"));
	if (args->depth > 0 || args->deepen_since || args->deepen_not)
		args->deepen = 1;
	if (server_supports("multi_ack_detailed")) {
		print_verbose(args, _("Server supports multi_ack_detailed"));
		multi_ack = 2;
		if (server_supports("no-done")) {
			print_verbose(args, _("Server supports no-done"));
			if (args->stateless_rpc)
				no_done = 1;
		}
	}
	else if (server_supports("multi_ack")) {
		print_verbose(args, _("Server supports multi_ack"));
		multi_ack = 1;
	}
	if (server_supports("side-band-64k")) {
		print_verbose(args, _("Server supports side-band-64k"));
		use_sideband = 2;
	}
	else if (server_supports("side-band")) {
		print_verbose(args, _("Server supports side-band"));
		use_sideband = 1;
	}
	if (server_supports("allow-tip-sha1-in-want")) {
		print_verbose(args, _("Server supports allow-tip-sha1-in-want"));
		allow_unadvertised_object_request |= ALLOW_TIP_SHA1;
	}
	if (server_supports("allow-reachable-sha1-in-want")) {
		print_verbose(args, _("Server supports allow-reachable-sha1-in-want"));
		allow_unadvertised_object_request |= ALLOW_REACHABLE_SHA1;
	}
	if (!server_supports("thin-pack"))
		args->use_thin_pack = 0;
	if (!server_supports("no-progress"))
		args->no_progress = 0;
	if (!server_supports("include-tag"))
		args->include_tag = 0;
	if (server_supports("ofs-delta"))
		print_verbose(args, _("Server supports ofs-delta"));
	else
		prefer_ofs_delta = 0;

	if (server_supports("filter")) {
		server_supports_filtering = 1;
		print_verbose(args, _("Server supports filter"));
	} else if (args->filter_options.choice) {
		warning("filtering not recognized by server, ignoring");
	}

	if ((agent_feature = server_feature_value("agent", &agent_len))) {
		agent_supported = 1;
		if (agent_len)
			print_verbose(args, _("Server version is %.*s"),
				      agent_len, agent_feature);
	}
	if (server_supports("deepen-since"))
		deepen_since_ok = 1;
	else if (args->deepen_since)
		die(_("Server does not support --shallow-since"));
	if (server_supports("deepen-not"))
		deepen_not_ok = 1;
	else if (args->deepen_not)
		die(_("Server does not support --shallow-exclude"));
	if (!server_supports("deepen-relative") && args->deepen_relative)
		die(_("Server does not support --deepen"));

	if (everything_local(args, &ref, sought, nr_sought)) {
		packet_flush(fd[1]);
		goto all_done;
	}
	if (find_common(args, fd, &oid, ref) < 0)
		if (!args->keep_pack)
			/* When cloning, it is not unusual to have
			 * no common commit.
			 */
			warning(_("no common commits"));

	if (args->stateless_rpc)
		packet_flush(fd[1]);
	if (args->deepen)
		setup_alternate_shallow(&shallow_lock, &alternate_shallow_file,
					NULL);
	else if (si->nr_ours || si->nr_theirs)
		alternate_shallow_file = setup_temporary_shallow(si->shallow);
	else
		alternate_shallow_file = NULL;
	if (get_pack(args, fd, pack_lockfile))
		die(_("git fetch-pack: fetch failed."));

 all_done:
	return ref;
}

static void fetch_pack_config(void)
{
	git_config_get_int("fetch.unpacklimit", &fetch_unpack_limit);
	git_config_get_int("transfer.unpacklimit", &transfer_unpack_limit);
	git_config_get_bool("repack.usedeltabaseoffset", &prefer_ofs_delta);
	git_config_get_bool("fetch.fsckobjects", &fetch_fsck_objects);
	git_config_get_bool("transfer.fsckobjects", &transfer_fsck_objects);

	git_config(git_default_config, NULL);
}

static void fetch_pack_setup(void)
{
	static int did_setup;
	if (did_setup)
		return;
	fetch_pack_config();
	if (0 <= transfer_unpack_limit)
		unpack_limit = transfer_unpack_limit;
	else if (0 <= fetch_unpack_limit)
		unpack_limit = fetch_unpack_limit;
	did_setup = 1;
}

static int remove_duplicates_in_refs(struct ref **ref, int nr)
{
	struct string_list names = STRING_LIST_INIT_NODUP;
	int src, dst;

	for (src = dst = 0; src < nr; src++) {
		struct string_list_item *item;
		item = string_list_insert(&names, ref[src]->name);
		if (item->util)
			continue; /* already have it */
		item->util = ref[src];
		if (src != dst)
			ref[dst] = ref[src];
		dst++;
	}
	for (src = dst; src < nr; src++)
		ref[src] = NULL;
	string_list_clear(&names, 0);
	return dst;
}

static void update_shallow(struct fetch_pack_args *args,
			   struct ref **sought, int nr_sought,
			   struct shallow_info *si)
{
	struct oid_array ref = OID_ARRAY_INIT;
	int *status;
	int i;

	if (args->deepen && alternate_shallow_file) {
		if (*alternate_shallow_file == '\0') { /* --unshallow */
			unlink_or_warn(git_path_shallow(the_repository));
			rollback_lock_file(&shallow_lock);
		} else
			commit_lock_file(&shallow_lock);
		return;
	}

	if (!si->shallow || !si->shallow->nr)
		return;

	if (args->cloning) {
		/*
		 * remote is shallow, but this is a clone, there are
		 * no objects in repo to worry about. Accept any
		 * shallow points that exist in the pack (iow in repo
		 * after get_pack() and reprepare_packed_git())
		 */
		struct oid_array extra = OID_ARRAY_INIT;
		struct object_id *oid = si->shallow->oid;
		for (i = 0; i < si->shallow->nr; i++)
			if (has_object_file(&oid[i]))
				oid_array_append(&extra, &oid[i]);
		if (extra.nr) {
			setup_alternate_shallow(&shallow_lock,
						&alternate_shallow_file,
						&extra);
			commit_lock_file(&shallow_lock);
		}
		oid_array_clear(&extra);
		return;
	}

	if (!si->nr_ours && !si->nr_theirs)
		return;

	remove_nonexistent_theirs_shallow(si);
	if (!si->nr_ours && !si->nr_theirs)
		return;
	for (i = 0; i < nr_sought; i++)
		oid_array_append(&ref, &sought[i]->old_oid);
	si->ref = &ref;

	if (args->update_shallow) {
		/*
		 * remote is also shallow, .git/shallow may be updated
		 * so all refs can be accepted. Make sure we only add
		 * shallow roots that are actually reachable from new
		 * refs.
		 */
		struct oid_array extra = OID_ARRAY_INIT;
		struct object_id *oid = si->shallow->oid;
		assign_shallow_commits_to_refs(si, NULL, NULL);
		if (!si->nr_ours && !si->nr_theirs) {
			oid_array_clear(&ref);
			return;
		}
		for (i = 0; i < si->nr_ours; i++)
			oid_array_append(&extra, &oid[si->ours[i]]);
		for (i = 0; i < si->nr_theirs; i++)
			oid_array_append(&extra, &oid[si->theirs[i]]);
		setup_alternate_shallow(&shallow_lock,
					&alternate_shallow_file,
					&extra);
		commit_lock_file(&shallow_lock);
		oid_array_clear(&extra);
		oid_array_clear(&ref);
		return;
	}

	/*
	 * remote is also shallow, check what ref is safe to update
	 * without updating .git/shallow
	 */
	status = xcalloc(nr_sought, sizeof(*status));
	assign_shallow_commits_to_refs(si, NULL, status);
	if (si->nr_ours || si->nr_theirs) {
		for (i = 0; i < nr_sought; i++)
			if (status[i])
				sought[i]->status = REF_STATUS_REJECT_SHALLOW;
	}
	free(status);
	oid_array_clear(&ref);
}

struct ref *fetch_pack(struct fetch_pack_args *args,
		       int fd[], struct child_process *conn,
		       const struct ref *ref,
		       const char *dest,
		       struct ref **sought, int nr_sought,
		       struct oid_array *shallow,
		       char **pack_lockfile)
{
	struct ref *ref_cpy;
	struct shallow_info si;

	fetch_pack_setup();
	if (nr_sought)
		nr_sought = remove_duplicates_in_refs(sought, nr_sought);

	if (!ref) {
		packet_flush(fd[1]);
		die(_("no matching remote head"));
	}
	prepare_shallow_info(&si, shallow);
	ref_cpy = do_fetch_pack(args, fd, ref, sought, nr_sought,
				&si, pack_lockfile);
	reprepare_packed_git(the_repository);
	update_shallow(args, sought, nr_sought, &si);
	clear_shallow_info(&si);
	return ref_cpy;
}

int report_unmatched_refs(struct ref **sought, int nr_sought)
{
	int i, ret = 0;

	for (i = 0; i < nr_sought; i++) {
		if (!sought[i])
			continue;
		switch (sought[i]->match_status) {
		case REF_MATCHED:
			continue;
		case REF_NOT_MATCHED:
			error(_("no such remote ref %s"), sought[i]->name);
			break;
		case REF_UNADVERTISED_NOT_ALLOWED:
			error(_("Server does not allow request for unadvertised object %s"),
			      sought[i]->name);
			break;
		}
		ret = 1;
	}
	return ret;
}