builtin-fetch-pack.c - git - Git at Google

 #include "cache.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"

 static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
 static int unpack_limit = 100;
 static struct fetch_pack_args args = {
 	/* .uploadpack = */ "git-upload-pack",
 };

 static const char fetch_pack_usage[] =
 "git-fetch-pack [--all] [--quiet|-q] [--keep|-k] [--thin] [--include-tag] [--upload-pack=<git-upload-pack>] [--depth=<n>] [--no-progress] [-v] [<host>:]<directory> [<refs>...]";

 #define COMPLETE	(1U << 0)
 #define COMMON		(1U << 1)
 #define COMMON_REF	(1U << 2)
 #define SEEN		(1U << 3)
 #define POPPED		(1U << 4)

 /*
  * 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 commit_list *rev_list;
 static int non_common_revs, multi_ack, use_sideband;

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

 		if (!(commit->object.parsed))
 			if (parse_commit(commit))
 				return;

 		insert_by_date(commit, &rev_list);

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

 static int rev_list_insert_ref(const char *path, const unsigned char *sha1, int flag, void *cb_data)
 {
 	struct object *o = deref_tag(parse_object(sha1), path, 0);

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

 	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 unsigned char* get_rev(void)
 {
 	struct commit *commit = NULL;

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

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

 		commit = rev_list->item;
 		if (!(commit->object.parsed))
 			if (!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;
 		}

 		rev_list = rev_list->next;
 	}

 	return commit->object.sha1;
 }

 static int find_common(int fd[2], unsigned char *result_sha1,
 		       struct ref *refs)
 {
 	int fetching;
 	int count = 0, flushes = 0, retval;
 	const unsigned char *sha1;
 	unsigned in_vain = 0;
 	int got_continue = 0;

 	for_each_ref(rev_list_insert_ref, NULL);

 	fetching = 0;
 	for ( ; refs ; refs = refs->next) {
 		unsigned char *remote = refs->old_sha1;
 		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)) != NULL) &&
 				(o->flags & COMPLETE)) {
 			continue;
 		}

 		if (!fetching)
 			packet_write(fd[1], "want %s%s%s%s%s%s%s%s\n",
 				     sha1_to_hex(remote),
 				     (multi_ack ? " multi_ack" : ""),
 				     (use_sideband == 2 ? " side-band-64k" : ""),
 				     (use_sideband == 1 ? " side-band" : ""),
 				     (args.use_thin_pack ? " thin-pack" : ""),
 				     (args.no_progress ? " no-progress" : ""),
 				     (args.include_tag ? " include-tag" : ""),
 				     " ofs-delta");
 		else
 			packet_write(fd[1], "want %s\n", sha1_to_hex(remote));
 		fetching++;
 	}
 	if (is_repository_shallow())
 		write_shallow_commits(fd[1], 1);
 	if (args.depth > 0)
 		packet_write(fd[1], "deepen %d", args.depth);
 	packet_flush(fd[1]);
 	if (!fetching)
 		return 1;

 	if (args.depth > 0) {
 		char line[1024];
 		unsigned char sha1[20];
 		int len;

 		while ((len = packet_read_line(fd[0], line, sizeof(line)))) {
 			if (!prefixcmp(line, "shallow ")) {
 				if (get_sha1_hex(line + 8, sha1))
 					die("invalid shallow line: %s", line);
 				register_shallow(sha1);
 				continue;
 			}
 			if (!prefixcmp(line, "unshallow ")) {
 				if (get_sha1_hex(line + 10, sha1))
 					die("invalid unshallow line: %s", line);
 				if (!lookup_object(sha1))
 					die("object not found: %s", line);
 				/* make sure that it is parsed as shallow */
 				if (!parse_object(sha1))
 					die("error in object: %s", line);
 				if (unregister_shallow(sha1))
 					die("no shallow found: %s", line);
 				continue;
 			}
 			die("expected shallow/unshallow, got %s", line);
 		}
 	}

 	flushes = 0;
 	retval = -1;
 	while ((sha1 = get_rev())) {
 		packet_write(fd[1], "have %s\n", sha1_to_hex(sha1));
 		if (args.verbose)
 			fprintf(stderr, "have %s\n", sha1_to_hex(sha1));
 		in_vain++;
 		if (!(31 & ++count)) {
 			int ack;

 			packet_flush(fd[1]);
 			flushes++;

 			/*
 			 * We keep one window "ahead" of the other side, and
 			 * will wait for an ACK only on the next one
 			 */
 			if (count == 32)
 				continue;

 			do {
 				ack = get_ack(fd[0], result_sha1);
 				if (args.verbose && ack)
 					fprintf(stderr, "got ack %d %s\n", ack,
 							sha1_to_hex(result_sha1));
 				if (ack == 1) {
 					flushes = 0;
 					multi_ack = 0;
 					retval = 0;
 					goto done;
 				} else if (ack == 2) {
 					struct commit *commit =
 						lookup_commit(result_sha1);
 					mark_common(commit, 0, 1);
 					retval = 0;
 					in_vain = 0;
 					got_continue = 1;
 				}
 			} while (ack);
 			flushes--;
 			if (got_continue && MAX_IN_VAIN < in_vain) {
 				if (args.verbose)
 					fprintf(stderr, "giving up\n");
 				break; /* give up */
 			}
 		}
 	}
 done:
 	packet_write(fd[1], "done\n");
 	if (args.verbose)
 		fprintf(stderr, "done\n");
 	if (retval != 0) {
 		multi_ack = 0;
 		flushes++;
 	}
 	while (flushes || multi_ack) {
 		int ack = get_ack(fd[0], result_sha1);
 		if (ack) {
 			if (args.verbose)
 				fprintf(stderr, "got ack (%d) %s\n", ack,
 					sha1_to_hex(result_sha1));
 			if (ack == 1)
 				return 0;
 			multi_ack = 1;
 			continue;
 		}
 		flushes--;
 	}
 	return retval;
 }

 static struct commit_list *complete;

 static int mark_complete(const char *path, const unsigned char *sha1, int flag, void *cb_data)
 {
 	struct object *o = parse_object(sha1);

 	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->sha1);
 	}
 	if (o && o->type == OBJ_COMMIT) {
 		struct commit *commit = (struct commit *)o;
 		commit->object.flags |= COMPLETE;
 		insert_by_date(commit, &complete);
 	}
 	return 0;
 }

 static void mark_recent_complete_commits(unsigned long cutoff)
 {
 	while (complete && cutoff <= complete->item->date) {
 		if (args.verbose)
 			fprintf(stderr, "Marking %s as complete\n",
 				sha1_to_hex(complete->item->object.sha1));
 		pop_most_recent_commit(&complete, COMPLETE);
 	}
 }

 static void filter_refs(struct ref **refs, int nr_match, char **match)
 {
 	struct ref **return_refs;
 	struct ref *newlist = NULL;
 	struct ref **newtail = &newlist;
 	struct ref *ref, *next;
 	struct ref *fastarray[32];

 	if (nr_match && !args.fetch_all) {
 		if (ARRAY_SIZE(fastarray) < nr_match)
 			return_refs = xcalloc(nr_match, sizeof(struct ref *));
 		else {
 			return_refs = fastarray;
 			memset(return_refs, 0, sizeof(struct ref *) * nr_match);
 		}
 	}
 	else
 		return_refs = NULL;

 	for (ref = *refs; ref; ref = next) {
 		next = ref->next;
 		if (!memcmp(ref->name, "refs/", 5) &&
 		    check_ref_format(ref->name + 5))
 			; /* trash */
 		else if (args.fetch_all &&
 			 (!args.depth || prefixcmp(ref->name, "refs/tags/") )) {
 			*newtail = ref;
 			ref->next = NULL;
 			newtail = &ref->next;
 			continue;
 		}
 		else {
 			int order = path_match(ref->name, nr_match, match);
 			if (order) {
 				return_refs[order-1] = ref;
 				continue; /* we will link it later */
 			}
 		}
 		free(ref);
 	}

 	if (!args.fetch_all) {
 		int i;
 		for (i = 0; i < nr_match; i++) {
 			ref = return_refs[i];
 			if (ref) {
 				*newtail = ref;
 				ref->next = NULL;
 				newtail = &ref->next;
 			}
 		}
 		if (return_refs != fastarray)
 			free(return_refs);
 	}
 	*refs = newlist;
 }

 static int everything_local(struct ref **refs, int nr_match, char **match)
 {
 	struct ref *ref;
 	int retval;
 	unsigned long cutoff = 0;

 	save_commit_buffer = 0;

 	for (ref = *refs; ref; ref = ref->next) {
 		struct object *o;

 		o = parse_object(ref->old_sha1);
 		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;
 		}
 	}

 	if (!args.depth) {
 		for_each_ref(mark_complete, NULL);
 		if (cutoff)
 			mark_recent_complete_commits(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_sha1),
 					     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(refs, nr_match, match);

 	for (retval = 1, ref = *refs; ref ; ref = ref->next) {
 		const unsigned char *remote = ref->old_sha1;
 		unsigned char local[20];
 		struct object *o;

 		o = lookup_object(remote);
 		if (!o || !(o->flags & COMPLETE)) {
 			retval = 0;
 			if (!args.verbose)
 				continue;
 			fprintf(stderr,
 				"want %s (%s)\n", sha1_to_hex(remote),
 				ref->name);
 			continue;
 		}

 		hashcpy(ref->new_sha1, local);
 		if (!args.verbose)
 			continue;
 		fprintf(stderr,
 			"already have %s (%s)\n", sha1_to_hex(remote),
 			ref->name);
 	}
 	return retval;
 }

 static int sideband_demux(int fd, void *data)
 {
 	int *xd = data;

 	return recv_sideband("fetch-pack", xd[0], fd, 2);
 }

 static int get_pack(int xd[2], char **pack_lockfile)
 {
 	struct async demux;
 	const char *argv[20];
 	char keep_arg[256];
 	char hdr_arg[256];
 	const char **av;
 	int do_keep = args.keep_pack;
 	struct child_process cmd;

 	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;
 		if (start_async(&demux))
 			die("fetch-pack: unable to fork off sideband"
 			    " demultiplexer");
 	}
 	else
 		demux.out = xd[0];

 	memset(&cmd, 0, sizeof(cmd));
 	cmd.argv = argv;
 	av = argv;
 	*hdr_arg = 0;
 	if (!args.keep_pack && unpack_limit) {
 		struct pack_header header;

 		if (read_pack_header(demux.out, &header))
 			die("protocol error: bad pack header");
 		snprintf(hdr_arg, sizeof(hdr_arg), "--pack_header=%u,%u",
 			 ntohl(header.hdr_version), ntohl(header.hdr_entries));
 		if (ntohl(header.hdr_entries) < unpack_limit)
 			do_keep = 0;
 		else
 			do_keep = 1;
 	}

 	if (do_keep) {
 		if (pack_lockfile)
 			cmd.out = -1;
 		*av++ = "index-pack";
 		*av++ = "--stdin";
 		if (!args.quiet && !args.no_progress)
 			*av++ = "-v";
 		if (args.use_thin_pack)
 			*av++ = "--fix-thin";
 		if (args.lock_pack || unpack_limit) {
 			int s = sprintf(keep_arg,
 					"--keep=fetch-pack %d on ", getpid());
 			if (gethostname(keep_arg + s, sizeof(keep_arg) - s))
 				strcpy(keep_arg + s, "localhost");
 			*av++ = keep_arg;
 		}
 	}
 	else {
 		*av++ = "unpack-objects";
 		if (args.quiet)
 			*av++ = "-q";
 	}
 	if (*hdr_arg)
 		*av++ = hdr_arg;
 	*av++ = NULL;

 	cmd.in = demux.out;
 	cmd.git_cmd = 1;
 	if (start_command(&cmd))
 		die("fetch-pack: unable to fork off %s", argv[0]);
 	if (do_keep && pack_lockfile) {
 		*pack_lockfile = index_pack_lockfile(cmd.out);
 		close(cmd.out);
 	}

 	if (finish_command(&cmd))
 		die("%s failed", argv[0]);
 	if (use_sideband && finish_async(&demux))
 		die("error in sideband demultiplexer");
 	return 0;
 }

 static struct ref *do_fetch_pack(int fd[2],
 		const struct ref *orig_ref,
 		int nr_match,
 		char **match,
 		char **pack_lockfile)
 {
 	struct ref *ref = copy_ref_list(orig_ref);
 	unsigned char sha1[20];

 	if (is_repository_shallow() && !server_supports("shallow"))
 		die("Server does not support shallow clients");
 	if (server_supports("multi_ack")) {
 		if (args.verbose)
 			fprintf(stderr, "Server supports multi_ack\n");
 		multi_ack = 1;
 	}
 	if (server_supports("side-band-64k")) {
 		if (args.verbose)
 			fprintf(stderr, "Server supports side-band-64k\n");
 		use_sideband = 2;
 	}
 	else if (server_supports("side-band")) {
 		if (args.verbose)
 			fprintf(stderr, "Server supports side-band\n");
 		use_sideband = 1;
 	}
 	if (everything_local(&ref, nr_match, match)) {
 		packet_flush(fd[1]);
 		goto all_done;
 	}
 	if (find_common(fd, sha1, ref) < 0)
 		if (!args.keep_pack)
 			/* When cloning, it is not unusual to have
 			 * no common commit.
 			 */
 			fprintf(stderr, "warning: no common commits\n");

 	if (get_pack(fd, pack_lockfile))
 		die("git-fetch-pack: fetch failed.");

  all_done:
 	return ref;
 }

 static int remove_duplicates(int nr_heads, char **heads)
 {
 	int src, dst;

 	for (src = dst = 0; src < nr_heads; src++) {
 		/* If heads[src] is different from any of
 		 * heads[0..dst], push it in.
 		 */
 		int i;
 		for (i = 0; i < dst; i++) {
 			if (!strcmp(heads[i], heads[src]))
 				break;
 		}
 		if (i < dst)
 			continue;
 		if (src != dst)
 			heads[dst] = heads[src];
 		dst++;
 	}
 	return dst;
 }

 static int fetch_pack_config(const char *var, const char *value)
 {
 	if (strcmp(var, "fetch.unpacklimit") == 0) {
 		fetch_unpack_limit = git_config_int(var, value);
 		return 0;
 	}

 	if (strcmp(var, "transfer.unpacklimit") == 0) {
 		transfer_unpack_limit = git_config_int(var, value);
 		return 0;
 	}

 	return git_default_config(var, value);
 }

 static struct lock_file lock;

 static void fetch_pack_setup(void)
 {
 	static int did_setup;
 	if (did_setup)
 		return;
 	git_config(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;
 }

 int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 {
 	int i, ret, nr_heads;
 	struct ref *ref = NULL;
 	char *dest = NULL, **heads;
 	int fd[2];
 	struct child_process *conn;

 	nr_heads = 0;
 	heads = NULL;
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];

 		if (*arg == '-') {
 			if (!prefixcmp(arg, "--upload-pack=")) {
 				args.uploadpack = arg + 14;
 				continue;
 			}
 			if (!prefixcmp(arg, "--exec=")) {
 				args.uploadpack = arg + 7;
 				continue;
 			}
 			if (!strcmp("--quiet", arg) || !strcmp("-q", arg)) {
 				args.quiet = 1;
 				continue;
 			}
 			if (!strcmp("--keep", arg) || !strcmp("-k", arg)) {
 				args.lock_pack = args.keep_pack;
 				args.keep_pack = 1;
 				continue;
 			}
 			if (!strcmp("--thin", arg)) {
 				args.use_thin_pack = 1;
 				continue;
 			}
 			if (!strcmp("--include-tag", arg)) {
 				args.include_tag = 1;
 				continue;
 			}
 			if (!strcmp("--all", arg)) {
 				args.fetch_all = 1;
 				continue;
 			}
 			if (!strcmp("-v", arg)) {
 				args.verbose = 1;
 				continue;
 			}
 			if (!prefixcmp(arg, "--depth=")) {
 				args.depth = strtol(arg + 8, NULL, 0);
 				continue;
 			}
 			if (!strcmp("--no-progress", arg)) {
 				args.no_progress = 1;
 				continue;
 			}
 			usage(fetch_pack_usage);
 		}
 		dest = (char *)arg;
 		heads = (char **)(argv + i + 1);
 		nr_heads = argc - i - 1;
 		break;
 	}
 	if (!dest)
 		usage(fetch_pack_usage);

 	conn = git_connect(fd, (char *)dest, args.uploadpack,
 			   args.verbose ? CONNECT_VERBOSE : 0);
 	if (conn) {
 		get_remote_heads(fd[0], &ref, 0, NULL, 0);

 		ref = fetch_pack(&args, fd, conn, ref, dest, nr_heads, heads, NULL);
 		close(fd[0]);
 		close(fd[1]);
 		if (finish_connect(conn))
 			ref = NULL;
 	} else {
 		ref = NULL;
 	}
 	ret = !ref;

 	if (!ret && nr_heads) {
 		/* If the heads to pull were given, we should have
 		 * consumed all of them by matching the remote.
 		 * Otherwise, 'git-fetch remote no-such-ref' would
 		 * silently succeed without issuing an error.
 		 */
 		for (i = 0; i < nr_heads; i++)
 			if (heads[i] && heads[i][0]) {
 				error("no such remote ref %s", heads[i]);
 				ret = 1;
 			}
 	}
 	while (ref) {
 		printf("%s %s\n",
 		       sha1_to_hex(ref->old_sha1), ref->name);
 		ref = ref->next;
 	}

 	return ret;
 }

 struct ref *fetch_pack(struct fetch_pack_args *my_args,
 		       int fd[], struct child_process *conn,
 		       const struct ref *ref,
 		const char *dest,
 		int nr_heads,
 		char **heads,
 		char **pack_lockfile)
 {
 	struct stat st;
 	struct ref *ref_cpy;

 	fetch_pack_setup();
 	memcpy(&args, my_args, sizeof(args));
 	if (args.depth > 0) {
 		if (stat(git_path("shallow"), &st))
 			st.st_mtime = 0;
 	}

 	if (heads && nr_heads)
 		nr_heads = remove_duplicates(nr_heads, heads);
 	if (!ref) {
 		packet_flush(fd[1]);
 		die("no matching remote head");
 	}
 	ref_cpy = do_fetch_pack(fd, ref, nr_heads, heads, pack_lockfile);

 	if (args.depth > 0) {
 		struct cache_time mtime;
 		char *shallow = git_path("shallow");
 		int fd;

 		mtime.sec = st.st_mtime;
 #ifdef USE_NSEC
 		mtime.usec = st.st_mtim.usec;
 #endif
 		if (stat(shallow, &st)) {
 			if (mtime.sec)
 				die("shallow file was removed during fetch");
 		} else if (st.st_mtime != mtime.sec
 #ifdef USE_NSEC
 				|| st.st_mtim.usec != mtime.usec
 #endif
 			  )
 			die("shallow file was changed during fetch");

 		fd = hold_lock_file_for_update(&lock, shallow, 1);
 		if (!write_shallow_commits(fd, 0)) {
 			unlink(shallow);
 			rollback_lock_file(&lock);
 		} else {
 			commit_lock_file(&lock);
 		}
 	}

 	return ref_cpy;
 }
	#include "cache.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"

	static int transfer_unpack_limit = -1;
	static int fetch_unpack_limit = -1;
	static int unpack_limit = 100;
	static struct fetch_pack_args args = {
	/* .uploadpack = */ "git-upload-pack",
	};

	static const char fetch_pack_usage[] =
	"git-fetch-pack [--all] [--quiet\|-q] [--keep\|-k] [--thin] [--include-tag] [--upload-pack=<git-upload-pack>] [--depth=<n>] [--no-progress] [-v] [<host>:]<directory> [<refs>...]";

	#define COMPLETE (1U << 0)
	#define COMMON (1U << 1)
	#define COMMON_REF (1U << 2)
	#define SEEN (1U << 3)
	#define POPPED (1U << 4)

	/*
	* 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 commit_list *rev_list;
	static int non_common_revs, multi_ack, use_sideband;

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

	if (!(commit->object.parsed))
	if (parse_commit(commit))
	return;

	insert_by_date(commit, &rev_list);

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

	static int rev_list_insert_ref(const char path, const unsigned char sha1, int flag, void *cb_data)
	{
	struct object *o = deref_tag(parse_object(sha1), path, 0);

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

	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 unsigned char* get_rev(void)
	{
	struct commit *commit = NULL;

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

	if (rev_list == NULL \|\| non_common_revs == 0)
	return NULL;

	commit = rev_list->item;
	if (!(commit->object.parsed))
	if (!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;
	}

	rev_list = rev_list->next;
	}

	return commit->object.sha1;
	}

	static int find_common(int fd[2], unsigned char *result_sha1,
	struct ref *refs)
	{
	int fetching;
	int count = 0, flushes = 0, retval;
	const unsigned char *sha1;
	unsigned in_vain = 0;
	int got_continue = 0;

	for_each_ref(rev_list_insert_ref, NULL);

	fetching = 0;
	for ( ; refs ; refs = refs->next) {
	unsigned char *remote = refs->old_sha1;
	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)) != NULL) &&
	(o->flags & COMPLETE)) {
	continue;
	}

	if (!fetching)
	packet_write(fd[1], "want %s%s%s%s%s%s%s%s\n",
	sha1_to_hex(remote),
	(multi_ack ? " multi_ack" : ""),
	(use_sideband == 2 ? " side-band-64k" : ""),
	(use_sideband == 1 ? " side-band" : ""),
	(args.use_thin_pack ? " thin-pack" : ""),
	(args.no_progress ? " no-progress" : ""),
	(args.include_tag ? " include-tag" : ""),
	" ofs-delta");
	else
	packet_write(fd[1], "want %s\n", sha1_to_hex(remote));
	fetching++;
	}
	if (is_repository_shallow())
	write_shallow_commits(fd[1], 1);
	if (args.depth > 0)
	packet_write(fd[1], "deepen %d", args.depth);
	packet_flush(fd[1]);
	if (!fetching)
	return 1;

	if (args.depth > 0) {
	char line[1024];
	unsigned char sha1[20];
	int len;

	while ((len = packet_read_line(fd[0], line, sizeof(line)))) {
	if (!prefixcmp(line, "shallow ")) {
	if (get_sha1_hex(line + 8, sha1))
	die("invalid shallow line: %s", line);
	register_shallow(sha1);
	continue;
	}
	if (!prefixcmp(line, "unshallow ")) {
	if (get_sha1_hex(line + 10, sha1))
	die("invalid unshallow line: %s", line);
	if (!lookup_object(sha1))
	die("object not found: %s", line);
	/* make sure that it is parsed as shallow */
	if (!parse_object(sha1))
	die("error in object: %s", line);
	if (unregister_shallow(sha1))
	die("no shallow found: %s", line);
	continue;
	}
	die("expected shallow/unshallow, got %s", line);
	}
	}

	flushes = 0;
	retval = -1;
	while ((sha1 = get_rev())) {
	packet_write(fd[1], "have %s\n", sha1_to_hex(sha1));
	if (args.verbose)
	fprintf(stderr, "have %s\n", sha1_to_hex(sha1));
	in_vain++;
	if (!(31 & ++count)) {
	int ack;

	packet_flush(fd[1]);
	flushes++;

	/*
	* We keep one window "ahead" of the other side, and
	* will wait for an ACK only on the next one
	*/
	if (count == 32)
	continue;

	do {
	ack = get_ack(fd[0], result_sha1);
	if (args.verbose && ack)
	fprintf(stderr, "got ack %d %s\n", ack,
	sha1_to_hex(result_sha1));
	if (ack == 1) {
	flushes = 0;
	multi_ack = 0;
	retval = 0;
	goto done;
	} else if (ack == 2) {
	struct commit *commit =
	lookup_commit(result_sha1);
	mark_common(commit, 0, 1);
	retval = 0;
	in_vain = 0;
	got_continue = 1;
	}
	} while (ack);
	flushes--;
	if (got_continue && MAX_IN_VAIN < in_vain) {
	if (args.verbose)
	fprintf(stderr, "giving up\n");
	break; /* give up */
	}
	}
	}
	done:
	packet_write(fd[1], "done\n");
	if (args.verbose)
	fprintf(stderr, "done\n");
	if (retval != 0) {
	multi_ack = 0;
	flushes++;
	}
	while (flushes \|\| multi_ack) {
	int ack = get_ack(fd[0], result_sha1);
	if (ack) {
	if (args.verbose)
	fprintf(stderr, "got ack (%d) %s\n", ack,
	sha1_to_hex(result_sha1));
	if (ack == 1)
	return 0;
	multi_ack = 1;
	continue;
	}
	flushes--;
	}
	return retval;
	}

	static struct commit_list *complete;

	static int mark_complete(const char path, const unsigned char sha1, int flag, void *cb_data)
	{
	struct object *o = parse_object(sha1);

	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->sha1);
	}
	if (o && o->type == OBJ_COMMIT) {
	struct commit commit = (struct commit )o;
	commit->object.flags \|= COMPLETE;
	insert_by_date(commit, &complete);
	}
	return 0;
	}

	static void mark_recent_complete_commits(unsigned long cutoff)
	{
	while (complete && cutoff <= complete->item->date) {
	if (args.verbose)
	fprintf(stderr, "Marking %s as complete\n",
	sha1_to_hex(complete->item->object.sha1));
	pop_most_recent_commit(&complete, COMPLETE);
	}
	}

	static void filter_refs(struct ref refs, int nr_match, char match)
	{
	struct ref **return_refs;
	struct ref *newlist = NULL;
	struct ref **newtail = &newlist;
	struct ref ref, next;
	struct ref *fastarray[32];

	if (nr_match && !args.fetch_all) {
	if (ARRAY_SIZE(fastarray) < nr_match)
	return_refs = xcalloc(nr_match, sizeof(struct ref *));
	else {
	return_refs = fastarray;
	memset(return_refs, 0, sizeof(struct ref ) nr_match);
	}
	}
	else
	return_refs = NULL;

	for (ref = *refs; ref; ref = next) {
	next = ref->next;
	if (!memcmp(ref->name, "refs/", 5) &&
	check_ref_format(ref->name + 5))
	; /* trash */
	else if (args.fetch_all &&
	(!args.depth \|\| prefixcmp(ref->name, "refs/tags/") )) {
	*newtail = ref;
	ref->next = NULL;
	newtail = &ref->next;
	continue;
	}
	else {
	int order = path_match(ref->name, nr_match, match);
	if (order) {
	return_refs[order-1] = ref;
	continue; /* we will link it later */
	}
	}
	free(ref);
	}

	if (!args.fetch_all) {
	int i;
	for (i = 0; i < nr_match; i++) {
	ref = return_refs[i];
	if (ref) {
	*newtail = ref;
	ref->next = NULL;
	newtail = &ref->next;
	}
	}
	if (return_refs != fastarray)
	free(return_refs);
	}
	*refs = newlist;
	}

	static int everything_local(struct ref refs, int nr_match, char match)
	{
	struct ref *ref;
	int retval;
	unsigned long cutoff = 0;

	save_commit_buffer = 0;

	for (ref = *refs; ref; ref = ref->next) {
	struct object *o;

	o = parse_object(ref->old_sha1);
	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;
	}
	}

	if (!args.depth) {
	for_each_ref(mark_complete, NULL);
	if (cutoff)
	mark_recent_complete_commits(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_sha1),
	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(refs, nr_match, match);

	for (retval = 1, ref = *refs; ref ; ref = ref->next) {
	const unsigned char *remote = ref->old_sha1;
	unsigned char local[20];
	struct object *o;

	o = lookup_object(remote);
	if (!o \|\| !(o->flags & COMPLETE)) {
	retval = 0;
	if (!args.verbose)
	continue;
	fprintf(stderr,
	"want %s (%s)\n", sha1_to_hex(remote),
	ref->name);
	continue;
	}

	hashcpy(ref->new_sha1, local);
	if (!args.verbose)
	continue;
	fprintf(stderr,
	"already have %s (%s)\n", sha1_to_hex(remote),
	ref->name);
	}
	return retval;
	}

	static int sideband_demux(int fd, void *data)
	{
	int *xd = data;

	return recv_sideband("fetch-pack", xd[0], fd, 2);
	}

	static int get_pack(int xd[2], char **pack_lockfile)
	{
	struct async demux;
	const char *argv[20];
	char keep_arg[256];
	char hdr_arg[256];
	const char **av;
	int do_keep = args.keep_pack;
	struct child_process cmd;

	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;
	if (start_async(&demux))
	die("fetch-pack: unable to fork off sideband"
	" demultiplexer");
	}
	else
	demux.out = xd[0];

	memset(&cmd, 0, sizeof(cmd));
	cmd.argv = argv;
	av = argv;
	*hdr_arg = 0;
	if (!args.keep_pack && unpack_limit) {
	struct pack_header header;

	if (read_pack_header(demux.out, &header))
	die("protocol error: bad pack header");
	snprintf(hdr_arg, sizeof(hdr_arg), "--pack_header=%u,%u",
	ntohl(header.hdr_version), ntohl(header.hdr_entries));
	if (ntohl(header.hdr_entries) < unpack_limit)
	do_keep = 0;
	else
	do_keep = 1;
	}

	if (do_keep) {
	if (pack_lockfile)
	cmd.out = -1;
	*av++ = "index-pack";
	*av++ = "--stdin";
	if (!args.quiet && !args.no_progress)
	*av++ = "-v";
	if (args.use_thin_pack)
	*av++ = "--fix-thin";
	if (args.lock_pack \|\| unpack_limit) {
	int s = sprintf(keep_arg,
	"--keep=fetch-pack %d on ", getpid());
	if (gethostname(keep_arg + s, sizeof(keep_arg) - s))
	strcpy(keep_arg + s, "localhost");
	*av++ = keep_arg;
	}
	}
	else {
	*av++ = "unpack-objects";
	if (args.quiet)
	*av++ = "-q";
	}
	if (*hdr_arg)
	*av++ = hdr_arg;
	*av++ = NULL;

	cmd.in = demux.out;
	cmd.git_cmd = 1;
	if (start_command(&cmd))
	die("fetch-pack: unable to fork off %s", argv[0]);
	if (do_keep && pack_lockfile) {
	*pack_lockfile = index_pack_lockfile(cmd.out);
	close(cmd.out);
	}

	if (finish_command(&cmd))
	die("%s failed", argv[0]);
	if (use_sideband && finish_async(&demux))
	die("error in sideband demultiplexer");
	return 0;
	}

	static struct ref *do_fetch_pack(int fd[2],
	const struct ref *orig_ref,
	int nr_match,
	char **match,
	char **pack_lockfile)
	{
	struct ref *ref = copy_ref_list(orig_ref);
	unsigned char sha1[20];

	if (is_repository_shallow() && !server_supports("shallow"))
	die("Server does not support shallow clients");
	if (server_supports("multi_ack")) {
	if (args.verbose)
	fprintf(stderr, "Server supports multi_ack\n");
	multi_ack = 1;
	}
	if (server_supports("side-band-64k")) {
	if (args.verbose)
	fprintf(stderr, "Server supports side-band-64k\n");
	use_sideband = 2;
	}
	else if (server_supports("side-band")) {
	if (args.verbose)
	fprintf(stderr, "Server supports side-band\n");
	use_sideband = 1;
	}
	if (everything_local(&ref, nr_match, match)) {
	packet_flush(fd[1]);
	goto all_done;
	}
	if (find_common(fd, sha1, ref) < 0)
	if (!args.keep_pack)
	/* When cloning, it is not unusual to have
	* no common commit.
	*/
	fprintf(stderr, "warning: no common commits\n");

	if (get_pack(fd, pack_lockfile))
	die("git-fetch-pack: fetch failed.");

	all_done:
	return ref;
	}

	static int remove_duplicates(int nr_heads, char **heads)
	{
	int src, dst;

	for (src = dst = 0; src < nr_heads; src++) {
	/* If heads[src] is different from any of
	* heads[0..dst], push it in.
	*/
	int i;
	for (i = 0; i < dst; i++) {
	if (!strcmp(heads[i], heads[src]))
	break;
	}
	if (i < dst)
	continue;
	if (src != dst)
	heads[dst] = heads[src];
	dst++;
	}
	return dst;
	}

	static int fetch_pack_config(const char var, const char value)
	{
	if (strcmp(var, "fetch.unpacklimit") == 0) {
	fetch_unpack_limit = git_config_int(var, value);
	return 0;
	}

	if (strcmp(var, "transfer.unpacklimit") == 0) {
	transfer_unpack_limit = git_config_int(var, value);
	return 0;
	}

	return git_default_config(var, value);
	}

	static struct lock_file lock;

	static void fetch_pack_setup(void)
	{
	static int did_setup;
	if (did_setup)
	return;
	git_config(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;
	}

	int cmd_fetch_pack(int argc, const char *argv, const char prefix)
	{
	int i, ret, nr_heads;
	struct ref *ref = NULL;
	char dest = NULL, *heads;
	int fd[2];
	struct child_process *conn;

	nr_heads = 0;
	heads = NULL;
	for (i = 1; i < argc; i++) {
	const char *arg = argv[i];

	if (*arg == '-') {
	if (!prefixcmp(arg, "--upload-pack=")) {
	args.uploadpack = arg + 14;
	continue;
	}
	if (!prefixcmp(arg, "--exec=")) {
	args.uploadpack = arg + 7;
	continue;
	}
	if (!strcmp("--quiet", arg) \|\| !strcmp("-q", arg)) {
	args.quiet = 1;
	continue;
	}
	if (!strcmp("--keep", arg) \|\| !strcmp("-k", arg)) {
	args.lock_pack = args.keep_pack;
	args.keep_pack = 1;
	continue;
	}
	if (!strcmp("--thin", arg)) {
	args.use_thin_pack = 1;
	continue;
	}
	if (!strcmp("--include-tag", arg)) {
	args.include_tag = 1;
	continue;
	}
	if (!strcmp("--all", arg)) {
	args.fetch_all = 1;
	continue;
	}
	if (!strcmp("-v", arg)) {
	args.verbose = 1;
	continue;
	}
	if (!prefixcmp(arg, "--depth=")) {
	args.depth = strtol(arg + 8, NULL, 0);
	continue;
	}
	if (!strcmp("--no-progress", arg)) {
	args.no_progress = 1;
	continue;
	}
	usage(fetch_pack_usage);
	}
	dest = (char *)arg;
	heads = (char **)(argv + i + 1);
	nr_heads = argc - i - 1;
	break;
	}
	if (!dest)
	usage(fetch_pack_usage);

	conn = git_connect(fd, (char *)dest, args.uploadpack,
	args.verbose ? CONNECT_VERBOSE : 0);
	if (conn) {
	get_remote_heads(fd[0], &ref, 0, NULL, 0);

	ref = fetch_pack(&args, fd, conn, ref, dest, nr_heads, heads, NULL);
	close(fd[0]);
	close(fd[1]);
	if (finish_connect(conn))
	ref = NULL;
	} else {
	ref = NULL;
	}
	ret = !ref;

	if (!ret && nr_heads) {
	/* If the heads to pull were given, we should have
	* consumed all of them by matching the remote.
	* Otherwise, 'git-fetch remote no-such-ref' would
	* silently succeed without issuing an error.
	*/
	for (i = 0; i < nr_heads; i++)
	if (heads[i] && heads[i][0]) {
	error("no such remote ref %s", heads[i]);
	ret = 1;
	}
	}
	while (ref) {
	printf("%s %s\n",
	sha1_to_hex(ref->old_sha1), ref->name);
	ref = ref->next;
	}

	return ret;
	}

	struct ref fetch_pack(struct fetch_pack_args my_args,
	int fd[], struct child_process *conn,
	const struct ref *ref,
	const char *dest,
	int nr_heads,
	char **heads,
	char **pack_lockfile)
	{
	struct stat st;
	struct ref *ref_cpy;

	fetch_pack_setup();
	memcpy(&args, my_args, sizeof(args));
	if (args.depth > 0) {
	if (stat(git_path("shallow"), &st))
	st.st_mtime = 0;
	}

	if (heads && nr_heads)
	nr_heads = remove_duplicates(nr_heads, heads);
	if (!ref) {
	packet_flush(fd[1]);
	die("no matching remote head");
	}
	ref_cpy = do_fetch_pack(fd, ref, nr_heads, heads, pack_lockfile);

	if (args.depth > 0) {
	struct cache_time mtime;
	char *shallow = git_path("shallow");
	int fd;

	mtime.sec = st.st_mtime;
	#ifdef USE_NSEC
	mtime.usec = st.st_mtim.usec;
	#endif
	if (stat(shallow, &st)) {
	if (mtime.sec)
	die("shallow file was removed during fetch");
	} else if (st.st_mtime != mtime.sec
	#ifdef USE_NSEC
	\|\| st.st_mtim.usec != mtime.usec
	#endif
	)
	die("shallow file was changed during fetch");

	fd = hold_lock_file_for_update(&lock, shallow, 1);
	if (!write_shallow_commits(fd, 0)) {
	unlink(shallow);
	rollback_lock_file(&lock);
	} else {
	commit_lock_file(&lock);
	}
	}

	return ref_cpy;
	}