Merge branch 'bc/sha-256-part-2'

[thirdparty/git.git] / builtin / receive-pack.c

#include "builtin.h"
#include "repository.h"
#include "config.h"
#include "lockfile.h"
#include "pack.h"
#include "refs.h"
#include "pkt-line.h"
#include "sideband.h"
#include "run-command.h"
#include "exec-cmd.h"
#include "commit.h"
#include "object.h"
#include "remote.h"
#include "connect.h"
#include "string-list.h"
#include "oid-array.h"
#include "connected.h"
#include "argv-array.h"
#include "version.h"
#include "tag.h"
#include "gpg-interface.h"
#include "sigchain.h"
#include "fsck.h"
#include "tmp-objdir.h"
#include "oidset.h"
#include "packfile.h"
#include "object-store.h"
#include "protocol.h"
#include "commit-reach.h"
#include "worktree.h"
#include "shallow.h"

static const char * const receive_pack_usage[] = {
	N_("git receive-pack <git-dir>"),
	NULL
};

enum deny_action {
	DENY_UNCONFIGURED,
	DENY_IGNORE,
	DENY_WARN,
	DENY_REFUSE,
	DENY_UPDATE_INSTEAD
};

static int deny_deletes;
static int deny_non_fast_forwards;
static enum deny_action deny_current_branch = DENY_UNCONFIGURED;
static enum deny_action deny_delete_current = DENY_UNCONFIGURED;
static int receive_fsck_objects = -1;
static int transfer_fsck_objects = -1;
static struct strbuf fsck_msg_types = STRBUF_INIT;
static int receive_unpack_limit = -1;
static int transfer_unpack_limit = -1;
static int advertise_atomic_push = 1;
static int advertise_push_options;
static int unpack_limit = 100;
static off_t max_input_size;
static int report_status;
static int use_sideband;
static int use_atomic;
static int use_push_options;
static int quiet;
static int prefer_ofs_delta = 1;
static int auto_update_server_info;
static int auto_gc = 1;
static int reject_thin;
static int stateless_rpc;
static const char *service_dir;
static const char *head_name;
static void *head_name_to_free;
static int sent_capabilities;
static int shallow_update;
static const char *alt_shallow_file;
static struct strbuf push_cert = STRBUF_INIT;
static struct object_id push_cert_oid;
static struct signature_check sigcheck;
static const char *push_cert_nonce;
static const char *cert_nonce_seed;

static const char *NONCE_UNSOLICITED = "UNSOLICITED";
static const char *NONCE_BAD = "BAD";
static const char *NONCE_MISSING = "MISSING";
static const char *NONCE_OK = "OK";
static const char *NONCE_SLOP = "SLOP";
static const char *nonce_status;
static long nonce_stamp_slop;
static timestamp_t nonce_stamp_slop_limit;
static struct ref_transaction *transaction;

static enum {
	KEEPALIVE_NEVER = 0,
	KEEPALIVE_AFTER_NUL,
	KEEPALIVE_ALWAYS
} use_keepalive;
static int keepalive_in_sec = 5;

static struct tmp_objdir *tmp_objdir;

static enum deny_action parse_deny_action(const char *var, const char *value)
{
	if (value) {
		if (!strcasecmp(value, "ignore"))
			return DENY_IGNORE;
		if (!strcasecmp(value, "warn"))
			return DENY_WARN;
		if (!strcasecmp(value, "refuse"))
			return DENY_REFUSE;
		if (!strcasecmp(value, "updateinstead"))
			return DENY_UPDATE_INSTEAD;
	}
	if (git_config_bool(var, value))
		return DENY_REFUSE;
	return DENY_IGNORE;
}

static int receive_pack_config(const char *var, const char *value, void *cb)
{
	int status = parse_hide_refs_config(var, value, "receive");

	if (status)
		return status;

	if (strcmp(var, "receive.denydeletes") == 0) {
		deny_deletes = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.denynonfastforwards") == 0) {
		deny_non_fast_forwards = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.unpacklimit") == 0) {
		receive_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;
	}

	if (strcmp(var, "receive.fsck.skiplist") == 0) {
		const char *path;

		if (git_config_pathname(&path, var, value))
			return 1;
		strbuf_addf(&fsck_msg_types, "%cskiplist=%s",
			fsck_msg_types.len ? ',' : '=', path);
		free((char *)path);
		return 0;
	}

	if (skip_prefix(var, "receive.fsck.", &var)) {
		if (is_valid_msg_type(var, value))
			strbuf_addf(&fsck_msg_types, "%c%s=%s",
				fsck_msg_types.len ? ',' : '=', var, value);
		else
			warning("Skipping unknown msg id '%s'", var);
		return 0;
	}

	if (strcmp(var, "receive.fsckobjects") == 0) {
		receive_fsck_objects = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "transfer.fsckobjects") == 0) {
		transfer_fsck_objects = git_config_bool(var, value);
		return 0;
	}

	if (!strcmp(var, "receive.denycurrentbranch")) {
		deny_current_branch = parse_deny_action(var, value);
		return 0;
	}

	if (strcmp(var, "receive.denydeletecurrent") == 0) {
		deny_delete_current = parse_deny_action(var, value);
		return 0;
	}

	if (strcmp(var, "repack.usedeltabaseoffset") == 0) {
		prefer_ofs_delta = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.updateserverinfo") == 0) {
		auto_update_server_info = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.autogc") == 0) {
		auto_gc = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.shallowupdate") == 0) {
		shallow_update = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.certnonceseed") == 0)
		return git_config_string(&cert_nonce_seed, var, value);

	if (strcmp(var, "receive.certnonceslop") == 0) {
		nonce_stamp_slop_limit = git_config_ulong(var, value);
		return 0;
	}

	if (strcmp(var, "receive.advertiseatomic") == 0) {
		advertise_atomic_push = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.advertisepushoptions") == 0) {
		advertise_push_options = git_config_bool(var, value);
		return 0;
	}

	if (strcmp(var, "receive.keepalive") == 0) {
		keepalive_in_sec = git_config_int(var, value);
		return 0;
	}

	if (strcmp(var, "receive.maxinputsize") == 0) {
		max_input_size = git_config_int64(var, value);
		return 0;
	}

	return git_default_config(var, value, cb);
}

static void show_ref(const char *path, const struct object_id *oid)
{
	if (sent_capabilities) {
		packet_write_fmt(1, "%s %s\n", oid_to_hex(oid), path);
	} else {
		struct strbuf cap = STRBUF_INIT;

		strbuf_addstr(&cap,
			      "report-status delete-refs side-band-64k quiet");
		if (advertise_atomic_push)
			strbuf_addstr(&cap, " atomic");
		if (prefer_ofs_delta)
			strbuf_addstr(&cap, " ofs-delta");
		if (push_cert_nonce)
			strbuf_addf(&cap, " push-cert=%s", push_cert_nonce);
		if (advertise_push_options)
			strbuf_addstr(&cap, " push-options");
		strbuf_addf(&cap, " object-format=%s", the_hash_algo->name);
		strbuf_addf(&cap, " agent=%s", git_user_agent_sanitized());
		packet_write_fmt(1, "%s %s%c%s\n",
			     oid_to_hex(oid), path, 0, cap.buf);
		strbuf_release(&cap);
		sent_capabilities = 1;
	}
}

static int show_ref_cb(const char *path_full, const struct object_id *oid,
		       int flag, void *data)
{
	struct oidset *seen = data;
	const char *path = strip_namespace(path_full);

	if (ref_is_hidden(path, path_full))
		return 0;

	/*
	 * Advertise refs outside our current namespace as ".have"
	 * refs, so that the client can use them to minimize data
	 * transfer but will otherwise ignore them.
	 */
	if (!path) {
		if (oidset_insert(seen, oid))
			return 0;
		path = ".have";
	} else {
		oidset_insert(seen, oid);
	}
	show_ref(path, oid);
	return 0;
}

static void show_one_alternate_ref(const struct object_id *oid,
				   void *data)
{
	struct oidset *seen = data;

	if (oidset_insert(seen, oid))
		return;

	show_ref(".have", oid);
}

static void write_head_info(void)
{
	static struct oidset seen = OIDSET_INIT;

	for_each_ref(show_ref_cb, &seen);
	for_each_alternate_ref(show_one_alternate_ref, &seen);
	oidset_clear(&seen);
	if (!sent_capabilities)
		show_ref("capabilities^{}", &null_oid);

	advertise_shallow_grafts(1);

	/* EOF */
	packet_flush(1);
}

struct command {
	struct command *next;
	const char *error_string;
	unsigned int skip_update:1,
		     did_not_exist:1;
	int index;
	struct object_id old_oid;
	struct object_id new_oid;
	char ref_name[FLEX_ARRAY]; /* more */
};

static void rp_error(const char *err, ...) __attribute__((format (printf, 1, 2)));
static void rp_warning(const char *err, ...) __attribute__((format (printf, 1, 2)));

static void report_message(const char *prefix, const char *err, va_list params)
{
	int sz;
	char msg[4096];

	sz = xsnprintf(msg, sizeof(msg), "%s", prefix);
	sz += vsnprintf(msg + sz, sizeof(msg) - sz, err, params);
	if (sz > (sizeof(msg) - 1))
		sz = sizeof(msg) - 1;
	msg[sz++] = '\n';

	if (use_sideband)
		send_sideband(1, 2, msg, sz, use_sideband);
	else
		xwrite(2, msg, sz);
}

static void rp_warning(const char *err, ...)
{
	va_list params;
	va_start(params, err);
	report_message("warning: ", err, params);
	va_end(params);
}

static void rp_error(const char *err, ...)
{
	va_list params;
	va_start(params, err);
	report_message("error: ", err, params);
	va_end(params);
}

static int copy_to_sideband(int in, int out, void *arg)
{
	char data[128];
	int keepalive_active = 0;

	if (keepalive_in_sec <= 0)
		use_keepalive = KEEPALIVE_NEVER;
	if (use_keepalive == KEEPALIVE_ALWAYS)
		keepalive_active = 1;

	while (1) {
		ssize_t sz;

		if (keepalive_active) {
			struct pollfd pfd;
			int ret;

			pfd.fd = in;
			pfd.events = POLLIN;
			ret = poll(&pfd, 1, 1000 * keepalive_in_sec);

			if (ret < 0) {
				if (errno == EINTR)
					continue;
				else
					break;
			} else if (ret == 0) {
				/* no data; send a keepalive packet */
				static const char buf[] = "0005\1";
				write_or_die(1, buf, sizeof(buf) - 1);
				continue;
			} /* else there is actual data to read */
		}

		sz = xread(in, data, sizeof(data));
		if (sz <= 0)
			break;

		if (use_keepalive == KEEPALIVE_AFTER_NUL && !keepalive_active) {
			const char *p = memchr(data, '\0', sz);
			if (p) {
				/*
				 * The NUL tells us to start sending keepalives. Make
				 * sure we send any other data we read along
				 * with it.
				 */
				keepalive_active = 1;
				send_sideband(1, 2, data, p - data, use_sideband);
				send_sideband(1, 2, p + 1, sz - (p - data + 1), use_sideband);
				continue;
			}
		}

		/*
		 * Either we're not looking for a NUL signal, or we didn't see
		 * it yet; just pass along the data.
		 */
		send_sideband(1, 2, data, sz, use_sideband);
	}
	close(in);
	return 0;
}

static void hmac_hash(unsigned char *out,
		      const char *key_in, size_t key_len,
		      const char *text, size_t text_len)
{
	unsigned char key[GIT_MAX_BLKSZ];
	unsigned char k_ipad[GIT_MAX_BLKSZ];
	unsigned char k_opad[GIT_MAX_BLKSZ];
	int i;
	git_hash_ctx ctx;

	/* RFC 2104 2. (1) */
	memset(key, '\0', GIT_MAX_BLKSZ);
	if (the_hash_algo->blksz < key_len) {
		the_hash_algo->init_fn(&ctx);
		the_hash_algo->update_fn(&ctx, key_in, key_len);
		the_hash_algo->final_fn(key, &ctx);
	} else {
		memcpy(key, key_in, key_len);
	}

	/* RFC 2104 2. (2) & (5) */
	for (i = 0; i < sizeof(key); i++) {
		k_ipad[i] = key[i] ^ 0x36;
		k_opad[i] = key[i] ^ 0x5c;
	}

	/* RFC 2104 2. (3) & (4) */
	the_hash_algo->init_fn(&ctx);
	the_hash_algo->update_fn(&ctx, k_ipad, sizeof(k_ipad));
	the_hash_algo->update_fn(&ctx, text, text_len);
	the_hash_algo->final_fn(out, &ctx);

	/* RFC 2104 2. (6) & (7) */
	the_hash_algo->init_fn(&ctx);
	the_hash_algo->update_fn(&ctx, k_opad, sizeof(k_opad));
	the_hash_algo->update_fn(&ctx, out, the_hash_algo->rawsz);
	the_hash_algo->final_fn(out, &ctx);
}

static char *prepare_push_cert_nonce(const char *path, timestamp_t stamp)
{
	struct strbuf buf = STRBUF_INIT;
	unsigned char hash[GIT_MAX_RAWSZ];

	strbuf_addf(&buf, "%s:%"PRItime, path, stamp);
	hmac_hash(hash, buf.buf, buf.len, cert_nonce_seed, strlen(cert_nonce_seed));
	strbuf_release(&buf);

	/* RFC 2104 5. HMAC-SHA1 or HMAC-SHA256 */
	strbuf_addf(&buf, "%"PRItime"-%.*s", stamp, (int)the_hash_algo->hexsz, hash_to_hex(hash));
	return strbuf_detach(&buf, NULL);
}

/*
 * NEEDSWORK: reuse find_commit_header() from jk/commit-author-parsing
 * after dropping "_commit" from its name and possibly moving it out
 * of commit.c
 */
static char *find_header(const char *msg, size_t len, const char *key,
			 const char **next_line)
{
	int key_len = strlen(key);
	const char *line = msg;

	while (line && line < msg + len) {
		const char *eol = strchrnul(line, '\n');

		if ((msg + len <= eol) || line == eol)
			return NULL;
		if (line + key_len < eol &&
		    !memcmp(line, key, key_len) && line[key_len] == ' ') {
			int offset = key_len + 1;
			if (next_line)
				*next_line = *eol ? eol + 1 : eol;
			return xmemdupz(line + offset, (eol - line) - offset);
		}
		line = *eol ? eol + 1 : NULL;
	}
	return NULL;
}

/*
 * Return zero if a and b are equal up to n bytes and nonzero if they are not.
 * This operation is guaranteed to run in constant time to avoid leaking data.
 */
static int constant_memequal(const char *a, const char *b, size_t n)
{
	int res = 0;
	size_t i;

	for (i = 0; i < n; i++)
		res |= a[i] ^ b[i];
	return res;
}

static const char *check_nonce(const char *buf, size_t len)
{
	char *nonce = find_header(buf, len, "nonce", NULL);
	timestamp_t stamp, ostamp;
	char *bohmac, *expect = NULL;
	const char *retval = NONCE_BAD;
	size_t noncelen;

	if (!nonce) {
		retval = NONCE_MISSING;
		goto leave;
	} else if (!push_cert_nonce) {
		retval = NONCE_UNSOLICITED;
		goto leave;
	} else if (!strcmp(push_cert_nonce, nonce)) {
		retval = NONCE_OK;
		goto leave;
	}

	if (!stateless_rpc) {
		/* returned nonce MUST match what we gave out earlier */
		retval = NONCE_BAD;
		goto leave;
	}

	/*
	 * In stateless mode, we may be receiving a nonce issued by
	 * another instance of the server that serving the same
	 * repository, and the timestamps may not match, but the
	 * nonce-seed and dir should match, so we can recompute and
	 * report the time slop.
	 *
	 * In addition, when a nonce issued by another instance has
	 * timestamp within receive.certnonceslop seconds, we pretend
	 * as if we issued that nonce when reporting to the hook.
	 */

	/* nonce is concat(<seconds-since-epoch>, "-", <hmac>) */
	if (*nonce <= '0' || '9' < *nonce) {
		retval = NONCE_BAD;
		goto leave;
	}
	stamp = parse_timestamp(nonce, &bohmac, 10);
	if (bohmac == nonce || bohmac[0] != '-') {
		retval = NONCE_BAD;
		goto leave;
	}

	noncelen = strlen(nonce);
	expect = prepare_push_cert_nonce(service_dir, stamp);
	if (noncelen != strlen(expect)) {
		/* This is not even the right size. */
		retval = NONCE_BAD;
		goto leave;
	}
	if (constant_memequal(expect, nonce, noncelen)) {
		/* Not what we would have signed earlier */
		retval = NONCE_BAD;
		goto leave;
	}

	/*
	 * By how many seconds is this nonce stale?  Negative value
	 * would mean it was issued by another server with its clock
	 * skewed in the future.
	 */
	ostamp = parse_timestamp(push_cert_nonce, NULL, 10);
	nonce_stamp_slop = (long)ostamp - (long)stamp;

	if (nonce_stamp_slop_limit &&
	    labs(nonce_stamp_slop) <= nonce_stamp_slop_limit) {
		/*
		 * Pretend as if the received nonce (which passes the
		 * HMAC check, so it is not a forged by third-party)
		 * is what we issued.
		 */
		free((void *)push_cert_nonce);
		push_cert_nonce = xstrdup(nonce);
		retval = NONCE_OK;
	} else {
		retval = NONCE_SLOP;
	}

leave:
	free(nonce);
	free(expect);
	return retval;
}

/*
 * Return 1 if there is no push_cert or if the push options in push_cert are
 * the same as those in the argument; 0 otherwise.
 */
static int check_cert_push_options(const struct string_list *push_options)
{
	const char *buf = push_cert.buf;
	int len = push_cert.len;

	char *option;
	const char *next_line;
	int options_seen = 0;

	int retval = 1;

	if (!len)
		return 1;

	while ((option = find_header(buf, len, "push-option", &next_line))) {
		len -= (next_line - buf);
		buf = next_line;
		options_seen++;
		if (options_seen > push_options->nr
		    || strcmp(option,
			      push_options->items[options_seen - 1].string)) {
			retval = 0;
			goto leave;
		}
		free(option);
	}

	if (options_seen != push_options->nr)
		retval = 0;

leave:
	free(option);
	return retval;
}

static void prepare_push_cert_sha1(struct child_process *proc)
{
	static int already_done;

	if (!push_cert.len)
		return;

	if (!already_done) {
		int bogs /* beginning_of_gpg_sig */;

		already_done = 1;
		if (write_object_file(push_cert.buf, push_cert.len, "blob",
				      &push_cert_oid))
			oidclr(&push_cert_oid);

		memset(&sigcheck, '\0', sizeof(sigcheck));

		bogs = parse_signature(push_cert.buf, push_cert.len);
		check_signature(push_cert.buf, bogs, push_cert.buf + bogs,
				push_cert.len - bogs, &sigcheck);

		nonce_status = check_nonce(push_cert.buf, bogs);
	}
	if (!is_null_oid(&push_cert_oid)) {
		argv_array_pushf(&proc->env_array, "GIT_PUSH_CERT=%s",
				 oid_to_hex(&push_cert_oid));
		argv_array_pushf(&proc->env_array, "GIT_PUSH_CERT_SIGNER=%s",
				 sigcheck.signer ? sigcheck.signer : "");
		argv_array_pushf(&proc->env_array, "GIT_PUSH_CERT_KEY=%s",
				 sigcheck.key ? sigcheck.key : "");
		argv_array_pushf(&proc->env_array, "GIT_PUSH_CERT_STATUS=%c",
				 sigcheck.result);
		if (push_cert_nonce) {
			argv_array_pushf(&proc->env_array,
					 "GIT_PUSH_CERT_NONCE=%s",
					 push_cert_nonce);
			argv_array_pushf(&proc->env_array,
					 "GIT_PUSH_CERT_NONCE_STATUS=%s",
					 nonce_status);
			if (nonce_status == NONCE_SLOP)
				argv_array_pushf(&proc->env_array,
						 "GIT_PUSH_CERT_NONCE_SLOP=%ld",
						 nonce_stamp_slop);
		}
	}
}

struct receive_hook_feed_state {
	struct command *cmd;
	int skip_broken;
	struct strbuf buf;
	const struct string_list *push_options;
};

typedef int (*feed_fn)(void *, const char **, size_t *);
static int run_and_feed_hook(const char *hook_name, feed_fn feed,
			     struct receive_hook_feed_state *feed_state)
{
	struct child_process proc = CHILD_PROCESS_INIT;
	struct async muxer;
	const char *argv[2];
	int code;

	argv[0] = find_hook(hook_name);
	if (!argv[0])
		return 0;

	argv[1] = NULL;

	proc.argv = argv;
	proc.in = -1;
	proc.stdout_to_stderr = 1;
	proc.trace2_hook_name = hook_name;

	if (feed_state->push_options) {
		int i;
		for (i = 0; i < feed_state->push_options->nr; i++)
			argv_array_pushf(&proc.env_array,
				"GIT_PUSH_OPTION_%d=%s", i,
				feed_state->push_options->items[i].string);
		argv_array_pushf(&proc.env_array, "GIT_PUSH_OPTION_COUNT=%d",
				 feed_state->push_options->nr);
	} else
		argv_array_pushf(&proc.env_array, "GIT_PUSH_OPTION_COUNT");

	if (tmp_objdir)
		argv_array_pushv(&proc.env_array, tmp_objdir_env(tmp_objdir));

	if (use_sideband) {
		memset(&muxer, 0, sizeof(muxer));
		muxer.proc = copy_to_sideband;
		muxer.in = -1;
		code = start_async(&muxer);
		if (code)
			return code;
		proc.err = muxer.in;
	}

	prepare_push_cert_sha1(&proc);

	code = start_command(&proc);
	if (code) {
		if (use_sideband)
			finish_async(&muxer);
		return code;
	}

	sigchain_push(SIGPIPE, SIG_IGN);

	while (1) {
		const char *buf;
		size_t n;
		if (feed(feed_state, &buf, &n))
			break;
		if (write_in_full(proc.in, buf, n) < 0)
			break;
	}
	close(proc.in);
	if (use_sideband)
		finish_async(&muxer);

	sigchain_pop(SIGPIPE);

	return finish_command(&proc);
}

static int feed_receive_hook(void *state_, const char **bufp, size_t *sizep)
{
	struct receive_hook_feed_state *state = state_;
	struct command *cmd = state->cmd;

	while (cmd &&
	       state->skip_broken && (cmd->error_string || cmd->did_not_exist))
		cmd = cmd->next;
	if (!cmd)
		return -1; /* EOF */
	strbuf_reset(&state->buf);
	strbuf_addf(&state->buf, "%s %s %s\n",
		    oid_to_hex(&cmd->old_oid), oid_to_hex(&cmd->new_oid),
		    cmd->ref_name);
	state->cmd = cmd->next;
	if (bufp) {
		*bufp = state->buf.buf;
		*sizep = state->buf.len;
	}
	return 0;
}

static int run_receive_hook(struct command *commands,
			    const char *hook_name,
			    int skip_broken,
			    const struct string_list *push_options)
{
	struct receive_hook_feed_state state;
	int status;

	strbuf_init(&state.buf, 0);
	state.cmd = commands;
	state.skip_broken = skip_broken;
	if (feed_receive_hook(&state, NULL, NULL))
		return 0;
	state.cmd = commands;
	state.push_options = push_options;
	status = run_and_feed_hook(hook_name, feed_receive_hook, &state);
	strbuf_release(&state.buf);
	return status;
}

static int run_update_hook(struct command *cmd)
{
	const char *argv[5];
	struct child_process proc = CHILD_PROCESS_INIT;
	int code;

	argv[0] = find_hook("update");
	if (!argv[0])
		return 0;

	argv[1] = cmd->ref_name;
	argv[2] = oid_to_hex(&cmd->old_oid);
	argv[3] = oid_to_hex(&cmd->new_oid);
	argv[4] = NULL;

	proc.no_stdin = 1;
	proc.stdout_to_stderr = 1;
	proc.err = use_sideband ? -1 : 0;
	proc.argv = argv;
	proc.trace2_hook_name = "update";

	code = start_command(&proc);
	if (code)
		return code;
	if (use_sideband)
		copy_to_sideband(proc.err, -1, NULL);
	return finish_command(&proc);
}

static char *refuse_unconfigured_deny_msg =
	N_("By default, updating the current branch in a non-bare repository\n"
	   "is denied, because it will make the index and work tree inconsistent\n"
	   "with what you pushed, and will require 'git reset --hard' to match\n"
	   "the work tree to HEAD.\n"
	   "\n"
	   "You can set the 'receive.denyCurrentBranch' configuration variable\n"
	   "to 'ignore' or 'warn' in the remote repository to allow pushing into\n"
	   "its current branch; however, this is not recommended unless you\n"
	   "arranged to update its work tree to match what you pushed in some\n"
	   "other way.\n"
	   "\n"
	   "To squelch this message and still keep the default behaviour, set\n"
	   "'receive.denyCurrentBranch' configuration variable to 'refuse'.");

static void refuse_unconfigured_deny(void)
{
	rp_error("%s", _(refuse_unconfigured_deny_msg));
}

static char *refuse_unconfigured_deny_delete_current_msg =
	N_("By default, deleting the current branch is denied, because the next\n"
	   "'git clone' won't result in any file checked out, causing confusion.\n"
	   "\n"
	   "You can set 'receive.denyDeleteCurrent' configuration variable to\n"
	   "'warn' or 'ignore' in the remote repository to allow deleting the\n"
	   "current branch, with or without a warning message.\n"
	   "\n"
	   "To squelch this message, you can set it to 'refuse'.");

static void refuse_unconfigured_deny_delete_current(void)
{
	rp_error("%s", _(refuse_unconfigured_deny_delete_current_msg));
}

static int command_singleton_iterator(void *cb_data, struct object_id *oid);
static int update_shallow_ref(struct command *cmd, struct shallow_info *si)
{
	struct shallow_lock shallow_lock = SHALLOW_LOCK_INIT;
	struct oid_array extra = OID_ARRAY_INIT;
	struct check_connected_options opt = CHECK_CONNECTED_INIT;
	uint32_t mask = 1 << (cmd->index % 32);
	int i;

	trace_printf_key(&trace_shallow,
			 "shallow: update_shallow_ref %s\n", cmd->ref_name);
	for (i = 0; i < si->shallow->nr; i++)
		if (si->used_shallow[i] &&
		    (si->used_shallow[i][cmd->index / 32] & mask) &&
		    !delayed_reachability_test(si, i))
			oid_array_append(&extra, &si->shallow->oid[i]);

	opt.env = tmp_objdir_env(tmp_objdir);
	setup_alternate_shallow(&shallow_lock, &opt.shallow_file, &extra);
	if (check_connected(command_singleton_iterator, cmd, &opt)) {
		rollback_shallow_file(the_repository, &shallow_lock);
		oid_array_clear(&extra);
		return -1;
	}

	commit_shallow_file(the_repository, &shallow_lock);

	/*
	 * Make sure setup_alternate_shallow() for the next ref does
	 * not lose these new roots..
	 */
	for (i = 0; i < extra.nr; i++)
		register_shallow(the_repository, &extra.oid[i]);

	si->shallow_ref[cmd->index] = 0;
	oid_array_clear(&extra);
	return 0;
}

/*
 * NEEDSWORK: we should consolidate various implementions of "are we
 * on an unborn branch?" test into one, and make the unified one more
 * robust. !get_sha1() based check used here and elsewhere would not
 * allow us to tell an unborn branch from corrupt ref, for example.
 * For the purpose of fixing "deploy-to-update does not work when
 * pushing into an empty repository" issue, this should suffice for
 * now.
 */
static int head_has_history(void)
{
	struct object_id oid;

	return !get_oid("HEAD", &oid);
}

static const char *push_to_deploy(unsigned char *sha1,
				  struct argv_array *env,
				  const char *work_tree)
{
	const char *update_refresh[] = {
		"update-index", "-q", "--ignore-submodules", "--refresh", NULL
	};
	const char *diff_files[] = {
		"diff-files", "--quiet", "--ignore-submodules", "--", NULL
	};
	const char *diff_index[] = {
		"diff-index", "--quiet", "--cached", "--ignore-submodules",
		NULL, "--", NULL
	};
	const char *read_tree[] = {
		"read-tree", "-u", "-m", NULL, NULL
	};
	struct child_process child = CHILD_PROCESS_INIT;

	child.argv = update_refresh;
	child.env = env->argv;
	child.dir = work_tree;
	child.no_stdin = 1;
	child.stdout_to_stderr = 1;
	child.git_cmd = 1;
	if (run_command(&child))
		return "Up-to-date check failed";

	/* run_command() does not clean up completely; reinitialize */
	child_process_init(&child);
	child.argv = diff_files;
	child.env = env->argv;
	child.dir = work_tree;
	child.no_stdin = 1;
	child.stdout_to_stderr = 1;
	child.git_cmd = 1;
	if (run_command(&child))
		return "Working directory has unstaged changes";

	/* diff-index with either HEAD or an empty tree */
	diff_index[4] = head_has_history() ? "HEAD" : empty_tree_oid_hex();

	child_process_init(&child);
	child.argv = diff_index;
	child.env = env->argv;
	child.no_stdin = 1;
	child.no_stdout = 1;
	child.stdout_to_stderr = 0;
	child.git_cmd = 1;
	if (run_command(&child))
		return "Working directory has staged changes";

	read_tree[3] = hash_to_hex(sha1);
	child_process_init(&child);
	child.argv = read_tree;
	child.env = env->argv;
	child.dir = work_tree;
	child.no_stdin = 1;
	child.no_stdout = 1;
	child.stdout_to_stderr = 0;
	child.git_cmd = 1;
	if (run_command(&child))
		return "Could not update working tree to new HEAD";

	return NULL;
}

static const char *push_to_checkout_hook = "push-to-checkout";

static const char *push_to_checkout(unsigned char *hash,
				    struct argv_array *env,
				    const char *work_tree)
{
	argv_array_pushf(env, "GIT_WORK_TREE=%s", absolute_path(work_tree));
	if (run_hook_le(env->argv, push_to_checkout_hook,
			hash_to_hex(hash), NULL))
		return "push-to-checkout hook declined";
	else
		return NULL;
}

static const char *update_worktree(unsigned char *sha1, const struct worktree *worktree)
{
	const char *retval, *work_tree, *git_dir = NULL;
	struct argv_array env = ARGV_ARRAY_INIT;

	if (worktree && worktree->path)
		work_tree = worktree->path;
	else if (git_work_tree_cfg)
		work_tree = git_work_tree_cfg;
	else
		work_tree = "..";

	if (is_bare_repository())
		return "denyCurrentBranch = updateInstead needs a worktree";
	if (worktree)
		git_dir = get_worktree_git_dir(worktree);
	if (!git_dir)
		git_dir = get_git_dir();

	argv_array_pushf(&env, "GIT_DIR=%s", absolute_path(git_dir));

	if (!find_hook(push_to_checkout_hook))
		retval = push_to_deploy(sha1, &env, work_tree);
	else
		retval = push_to_checkout(sha1, &env, work_tree);

	argv_array_clear(&env);
	return retval;
}

static const char *update(struct command *cmd, struct shallow_info *si)
{
	const char *name = cmd->ref_name;
	struct strbuf namespaced_name_buf = STRBUF_INIT;
	static char *namespaced_name;
	const char *ret;
	struct object_id *old_oid = &cmd->old_oid;
	struct object_id *new_oid = &cmd->new_oid;
	int do_update_worktree = 0;
	const struct worktree *worktree = is_bare_repository() ? NULL : find_shared_symref("HEAD", name);

	/* only refs/... are allowed */
	if (!starts_with(name, "refs/") || check_refname_format(name + 5, 0)) {
		rp_error("refusing to create funny ref '%s' remotely", name);
		return "funny refname";
	}

	strbuf_addf(&namespaced_name_buf, "%s%s", get_git_namespace(), name);
	free(namespaced_name);
	namespaced_name = strbuf_detach(&namespaced_name_buf, NULL);

	if (worktree) {
		switch (deny_current_branch) {
		case DENY_IGNORE:
			break;
		case DENY_WARN:
			rp_warning("updating the current branch");
			break;
		case DENY_REFUSE:
		case DENY_UNCONFIGURED:
			rp_error("refusing to update checked out branch: %s", name);
			if (deny_current_branch == DENY_UNCONFIGURED)
				refuse_unconfigured_deny();
			return "branch is currently checked out";
		case DENY_UPDATE_INSTEAD:
			/* pass -- let other checks intervene first */
			do_update_worktree = 1;
			break;
		}
	}

	if (!is_null_oid(new_oid) && !has_object_file(new_oid)) {
		error("unpack should have generated %s, "
		      "but I can't find it!", oid_to_hex(new_oid));
		return "bad pack";
	}

	if (!is_null_oid(old_oid) && is_null_oid(new_oid)) {
		if (deny_deletes && starts_with(name, "refs/heads/")) {
			rp_error("denying ref deletion for %s", name);
			return "deletion prohibited";
		}

		if (worktree || (head_name && !strcmp(namespaced_name, head_name))) {
			switch (deny_delete_current) {
			case DENY_IGNORE:
				break;
			case DENY_WARN:
				rp_warning("deleting the current branch");
				break;
			case DENY_REFUSE:
			case DENY_UNCONFIGURED:
			case DENY_UPDATE_INSTEAD:
				if (deny_delete_current == DENY_UNCONFIGURED)
					refuse_unconfigured_deny_delete_current();
				rp_error("refusing to delete the current branch: %s", name);
				return "deletion of the current branch prohibited";
			default:
				return "Invalid denyDeleteCurrent setting";
			}
		}
	}

	if (deny_non_fast_forwards && !is_null_oid(new_oid) &&
	    !is_null_oid(old_oid) &&
	    starts_with(name, "refs/heads/")) {
		struct object *old_object, *new_object;
		struct commit *old_commit, *new_commit;

		old_object = parse_object(the_repository, old_oid);
		new_object = parse_object(the_repository, new_oid);

		if (!old_object || !new_object ||
		    old_object->type != OBJ_COMMIT ||
		    new_object->type != OBJ_COMMIT) {
			error("bad sha1 objects for %s", name);
			return "bad ref";
		}
		old_commit = (struct commit *)old_object;
		new_commit = (struct commit *)new_object;
		if (!in_merge_bases(old_commit, new_commit)) {
			rp_error("denying non-fast-forward %s"
				 " (you should pull first)", name);
			return "non-fast-forward";
		}
	}
	if (run_update_hook(cmd)) {
		rp_error("hook declined to update %s", name);
		return "hook declined";
	}

	if (do_update_worktree) {
		ret = update_worktree(new_oid->hash, find_shared_symref("HEAD", name));
		if (ret)
			return ret;
	}

	if (is_null_oid(new_oid)) {
		struct strbuf err = STRBUF_INIT;
		if (!parse_object(the_repository, old_oid)) {
			old_oid = NULL;
			if (ref_exists(name)) {
				rp_warning("Allowing deletion of corrupt ref.");
			} else {
				rp_warning("Deleting a non-existent ref.");
				cmd->did_not_exist = 1;
			}
		}
		if (ref_transaction_delete(transaction,
					   namespaced_name,
					   old_oid,
					   0, "push", &err)) {
			rp_error("%s", err.buf);
			strbuf_release(&err);
			return "failed to delete";
		}
		strbuf_release(&err);
		return NULL; /* good */
	}
	else {
		struct strbuf err = STRBUF_INIT;
		if (shallow_update && si->shallow_ref[cmd->index] &&
		    update_shallow_ref(cmd, si))
			return "shallow error";

		if (ref_transaction_update(transaction,
					   namespaced_name,
					   new_oid, old_oid,
					   0, "push",
					   &err)) {
			rp_error("%s", err.buf);
			strbuf_release(&err);

			return "failed to update ref";
		}
		strbuf_release(&err);

		return NULL; /* good */
	}
}

static void run_update_post_hook(struct command *commands)
{
	struct command *cmd;
	struct child_process proc = CHILD_PROCESS_INIT;
	const char *hook;

	hook = find_hook("post-update");
	if (!hook)
		return;

	for (cmd = commands; cmd; cmd = cmd->next) {
		if (cmd->error_string || cmd->did_not_exist)
			continue;
		if (!proc.args.argc)
			argv_array_push(&proc.args, hook);
		argv_array_push(&proc.args, cmd->ref_name);
	}
	if (!proc.args.argc)
		return;

	proc.no_stdin = 1;
	proc.stdout_to_stderr = 1;
	proc.err = use_sideband ? -1 : 0;
	proc.trace2_hook_name = "post-update";

	if (!start_command(&proc)) {
		if (use_sideband)
			copy_to_sideband(proc.err, -1, NULL);
		finish_command(&proc);
	}
}

static void check_aliased_update_internal(struct command *cmd,
					  struct string_list *list,
					  const char *dst_name, int flag)
{
	struct string_list_item *item;
	struct command *dst_cmd;

	if (!(flag & REF_ISSYMREF))
		return;

	if (!dst_name) {
		rp_error("refusing update to broken symref '%s'", cmd->ref_name);
		cmd->skip_update = 1;
		cmd->error_string = "broken symref";
		return;
	}
	dst_name = strip_namespace(dst_name);

	if ((item = string_list_lookup(list, dst_name)) == NULL)
		return;

	cmd->skip_update = 1;

	dst_cmd = (struct command *) item->util;

	if (oideq(&cmd->old_oid, &dst_cmd->old_oid) &&
	    oideq(&cmd->new_oid, &dst_cmd->new_oid))
		return;

	dst_cmd->skip_update = 1;

	rp_error("refusing inconsistent update between symref '%s' (%s..%s) and"
		 " its target '%s' (%s..%s)",
		 cmd->ref_name,
		 find_unique_abbrev(&cmd->old_oid, DEFAULT_ABBREV),
		 find_unique_abbrev(&cmd->new_oid, DEFAULT_ABBREV),
		 dst_cmd->ref_name,
		 find_unique_abbrev(&dst_cmd->old_oid, DEFAULT_ABBREV),
		 find_unique_abbrev(&dst_cmd->new_oid, DEFAULT_ABBREV));

	cmd->error_string = dst_cmd->error_string =
		"inconsistent aliased update";
}

static void check_aliased_update(struct command *cmd, struct string_list *list)
{
	struct strbuf buf = STRBUF_INIT;
	const char *dst_name;
	int flag;

	strbuf_addf(&buf, "%s%s", get_git_namespace(), cmd->ref_name);
	dst_name = resolve_ref_unsafe(buf.buf, 0, NULL, &flag);
	check_aliased_update_internal(cmd, list, dst_name, flag);
	strbuf_release(&buf);
}

static void check_aliased_updates(struct command *commands)
{
	struct command *cmd;
	struct string_list ref_list = STRING_LIST_INIT_NODUP;

	for (cmd = commands; cmd; cmd = cmd->next) {
		struct string_list_item *item =
			string_list_append(&ref_list, cmd->ref_name);
		item->util = (void *)cmd;
	}
	string_list_sort(&ref_list);

	for (cmd = commands; cmd; cmd = cmd->next) {
		if (!cmd->error_string)
			check_aliased_update(cmd, &ref_list);
	}

	string_list_clear(&ref_list, 0);
}

static int command_singleton_iterator(void *cb_data, struct object_id *oid)
{
	struct command **cmd_list = cb_data;
	struct command *cmd = *cmd_list;

	if (!cmd || is_null_oid(&cmd->new_oid))
		return -1; /* end of list */
	*cmd_list = NULL; /* this returns only one */
	oidcpy(oid, &cmd->new_oid);
	return 0;
}

static void set_connectivity_errors(struct command *commands,
				    struct shallow_info *si)
{
	struct command *cmd;

	for (cmd = commands; cmd; cmd = cmd->next) {
		struct command *singleton = cmd;
		struct check_connected_options opt = CHECK_CONNECTED_INIT;

		if (shallow_update && si->shallow_ref[cmd->index])
			/* to be checked in update_shallow_ref() */
			continue;

		opt.env = tmp_objdir_env(tmp_objdir);
		if (!check_connected(command_singleton_iterator, &singleton,
				     &opt))
			continue;

		cmd->error_string = "missing necessary objects";
	}
}

struct iterate_data {
	struct command *cmds;
	struct shallow_info *si;
};

static int iterate_receive_command_list(void *cb_data, struct object_id *oid)
{
	struct iterate_data *data = cb_data;
	struct command **cmd_list = &data->cmds;
	struct command *cmd = *cmd_list;

	for (; cmd; cmd = cmd->next) {
		if (shallow_update && data->si->shallow_ref[cmd->index])
			/* to be checked in update_shallow_ref() */
			continue;
		if (!is_null_oid(&cmd->new_oid) && !cmd->skip_update) {
			oidcpy(oid, &cmd->new_oid);
			*cmd_list = cmd->next;
			return 0;
		}
	}
	*cmd_list = NULL;
	return -1; /* end of list */
}

static void reject_updates_to_hidden(struct command *commands)
{
	struct strbuf refname_full = STRBUF_INIT;
	size_t prefix_len;
	struct command *cmd;

	strbuf_addstr(&refname_full, get_git_namespace());
	prefix_len = refname_full.len;

	for (cmd = commands; cmd; cmd = cmd->next) {
		if (cmd->error_string)
			continue;

		strbuf_setlen(&refname_full, prefix_len);
		strbuf_addstr(&refname_full, cmd->ref_name);

		if (!ref_is_hidden(cmd->ref_name, refname_full.buf))
			continue;
		if (is_null_oid(&cmd->new_oid))
			cmd->error_string = "deny deleting a hidden ref";
		else
			cmd->error_string = "deny updating a hidden ref";
	}

	strbuf_release(&refname_full);
}

static int should_process_cmd(struct command *cmd)
{
	return !cmd->error_string && !cmd->skip_update;
}

static void warn_if_skipped_connectivity_check(struct command *commands,
					       struct shallow_info *si)
{
	struct command *cmd;
	int checked_connectivity = 1;

	for (cmd = commands; cmd; cmd = cmd->next) {
		if (should_process_cmd(cmd) && si->shallow_ref[cmd->index]) {
			error("BUG: connectivity check has not been run on ref %s",
			      cmd->ref_name);
			checked_connectivity = 0;
		}
	}
	if (!checked_connectivity)
		BUG("connectivity check skipped???");
}

static void execute_commands_non_atomic(struct command *commands,
					struct shallow_info *si)
{
	struct command *cmd;
	struct strbuf err = STRBUF_INIT;

	for (cmd = commands; cmd; cmd = cmd->next) {
		if (!should_process_cmd(cmd))
			continue;

		transaction = ref_transaction_begin(&err);
		if (!transaction) {
			rp_error("%s", err.buf);
			strbuf_reset(&err);
			cmd->error_string = "transaction failed to start";
			continue;
		}

		cmd->error_string = update(cmd, si);

		if (!cmd->error_string
		    && ref_transaction_commit(transaction, &err)) {
			rp_error("%s", err.buf);
			strbuf_reset(&err);
			cmd->error_string = "failed to update ref";
		}
		ref_transaction_free(transaction);
	}
	strbuf_release(&err);
}

static void execute_commands_atomic(struct command *commands,
					struct shallow_info *si)
{
	struct command *cmd;
	struct strbuf err = STRBUF_INIT;
	const char *reported_error = "atomic push failure";

	transaction = ref_transaction_begin(&err);
	if (!transaction) {
		rp_error("%s", err.buf);
		strbuf_reset(&err);
		reported_error = "transaction failed to start";
		goto failure;
	}

	for (cmd = commands; cmd; cmd = cmd->next) {
		if (!should_process_cmd(cmd))
			continue;

		cmd->error_string = update(cmd, si);

		if (cmd->error_string)
			goto failure;
	}

	if (ref_transaction_commit(transaction, &err)) {
		rp_error("%s", err.buf);
		reported_error = "atomic transaction failed";
		goto failure;
	}
	goto cleanup;

failure:
	for (cmd = commands; cmd; cmd = cmd->next)
		if (!cmd->error_string)
			cmd->error_string = reported_error;

cleanup:
	ref_transaction_free(transaction);
	strbuf_release(&err);
}

static void execute_commands(struct command *commands,
			     const char *unpacker_error,
			     struct shallow_info *si,
			     const struct string_list *push_options)
{
	struct check_connected_options opt = CHECK_CONNECTED_INIT;
	struct command *cmd;
	struct iterate_data data;
	struct async muxer;
	int err_fd = 0;

	if (unpacker_error) {
		for (cmd = commands; cmd; cmd = cmd->next)
			cmd->error_string = "unpacker error";
		return;
	}

	if (use_sideband) {
		memset(&muxer, 0, sizeof(muxer));
		muxer.proc = copy_to_sideband;
		muxer.in = -1;
		if (!start_async(&muxer))
			err_fd = muxer.in;
		/* ...else, continue without relaying sideband */
	}

	data.cmds = commands;
	data.si = si;
	opt.err_fd = err_fd;
	opt.progress = err_fd && !quiet;
	opt.env = tmp_objdir_env(tmp_objdir);
	if (check_connected(iterate_receive_command_list, &data, &opt))
		set_connectivity_errors(commands, si);

	if (use_sideband)
		finish_async(&muxer);

	reject_updates_to_hidden(commands);

	if (run_receive_hook(commands, "pre-receive", 0, push_options)) {
		for (cmd = commands; cmd; cmd = cmd->next) {
			if (!cmd->error_string)
				cmd->error_string = "pre-receive hook declined";
		}
		return;
	}

	/*
	 * Now we'll start writing out refs, which means the objects need
	 * to be in their final positions so that other processes can see them.
	 */
	if (tmp_objdir_migrate(tmp_objdir) < 0) {
		for (cmd = commands; cmd; cmd = cmd->next) {
			if (!cmd->error_string)
				cmd->error_string = "unable to migrate objects to permanent storage";
		}
		return;
	}
	tmp_objdir = NULL;

	check_aliased_updates(commands);

	free(head_name_to_free);
	head_name = head_name_to_free = resolve_refdup("HEAD", 0, NULL, NULL);

	if (use_atomic)
		execute_commands_atomic(commands, si);
	else
		execute_commands_non_atomic(commands, si);

	if (shallow_update)
		warn_if_skipped_connectivity_check(commands, si);
}

static struct command **queue_command(struct command **tail,
				      const char *line,
				      int linelen)
{
	struct object_id old_oid, new_oid;
	struct command *cmd;
	const char *refname;
	int reflen;
	const char *p;

	if (parse_oid_hex(line, &old_oid, &p) ||
	    *p++ != ' ' ||
	    parse_oid_hex(p, &new_oid, &p) ||
	    *p++ != ' ')
		die("protocol error: expected old/new/ref, got '%s'", line);

	refname = p;
	reflen = linelen - (p - line);
	FLEX_ALLOC_MEM(cmd, ref_name, refname, reflen);
	oidcpy(&cmd->old_oid, &old_oid);
	oidcpy(&cmd->new_oid, &new_oid);
	*tail = cmd;
	return &cmd->next;
}

static void queue_commands_from_cert(struct command **tail,
				     struct strbuf *push_cert)
{
	const char *boc, *eoc;

	if (*tail)
		die("protocol error: got both push certificate and unsigned commands");

	boc = strstr(push_cert->buf, "\n\n");
	if (!boc)
		die("malformed push certificate %.*s", 100, push_cert->buf);
	else
		boc += 2;
	eoc = push_cert->buf + parse_signature(push_cert->buf, push_cert->len);

	while (boc < eoc) {
		const char *eol = memchr(boc, '\n', eoc - boc);
		tail = queue_command(tail, boc, eol ? eol - boc : eoc - boc);
		boc = eol ? eol + 1 : eoc;
	}
}

static struct command *read_head_info(struct packet_reader *reader,
				      struct oid_array *shallow)
{
	struct command *commands = NULL;
	struct command **p = &commands;
	for (;;) {
		int linelen;

		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
			break;

		if (reader->pktlen > 8 && starts_with(reader->line, "shallow ")) {
			struct object_id oid;
			if (get_oid_hex(reader->line + 8, &oid))
				die("protocol error: expected shallow sha, got '%s'",
				    reader->line + 8);
			oid_array_append(shallow, &oid);
			continue;
		}

		linelen = strlen(reader->line);
		if (linelen < reader->pktlen) {
			const char *feature_list = reader->line + linelen + 1;
			const char *hash = NULL;
			int len = 0;
			if (parse_feature_request(feature_list, "report-status"))
				report_status = 1;
			if (parse_feature_request(feature_list, "side-band-64k"))
				use_sideband = LARGE_PACKET_MAX;
			if (parse_feature_request(feature_list, "quiet"))
				quiet = 1;
			if (advertise_atomic_push
			    && parse_feature_request(feature_list, "atomic"))
				use_atomic = 1;
			if (advertise_push_options
			    && parse_feature_request(feature_list, "push-options"))
				use_push_options = 1;
			hash = parse_feature_value(feature_list, "object-format", &len, NULL);
			if (!hash) {
				hash = hash_algos[GIT_HASH_SHA1].name;
				len = strlen(hash);
			}
			if (xstrncmpz(the_hash_algo->name, hash, len))
				die("error: unsupported object format '%s'", hash);
		}

		if (!strcmp(reader->line, "push-cert")) {
			int true_flush = 0;
			int saved_options = reader->options;
			reader->options &= ~PACKET_READ_CHOMP_NEWLINE;

			for (;;) {
				packet_reader_read(reader);
				if (reader->status == PACKET_READ_FLUSH) {
					true_flush = 1;
					break;
				}
				if (reader->status != PACKET_READ_NORMAL) {
					die("protocol error: got an unexpected packet");
				}
				if (!strcmp(reader->line, "push-cert-end\n"))
					break; /* end of cert */
				strbuf_addstr(&push_cert, reader->line);
			}
			reader->options = saved_options;

			if (true_flush)
				break;
			continue;
		}

		p = queue_command(p, reader->line, linelen);
	}

	if (push_cert.len)
		queue_commands_from_cert(p, &push_cert);

	return commands;
}

static void read_push_options(struct packet_reader *reader,
			      struct string_list *options)
{
	while (1) {
		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
			break;

		string_list_append(options, reader->line);
	}
}

static const char *parse_pack_header(struct pack_header *hdr)
{
	switch (read_pack_header(0, hdr)) {
	case PH_ERROR_EOF:
		return "eof before pack header was fully read";

	case PH_ERROR_PACK_SIGNATURE:
		return "protocol error (pack signature mismatch detected)";

	case PH_ERROR_PROTOCOL:
		return "protocol error (pack version unsupported)";

	default:
		return "unknown error in parse_pack_header";

	case 0:
		return NULL;
	}
}

static const char *pack_lockfile;

static void push_header_arg(struct argv_array *args, struct pack_header *hdr)
{
	argv_array_pushf(args, "--pack_header=%"PRIu32",%"PRIu32,
			ntohl(hdr->hdr_version), ntohl(hdr->hdr_entries));
}

static const char *unpack(int err_fd, struct shallow_info *si)
{
	struct pack_header hdr;
	const char *hdr_err;
	int status;
	struct child_process child = CHILD_PROCESS_INIT;
	int fsck_objects = (receive_fsck_objects >= 0
			    ? receive_fsck_objects
			    : transfer_fsck_objects >= 0
			    ? transfer_fsck_objects
			    : 0);

	hdr_err = parse_pack_header(&hdr);
	if (hdr_err) {
		if (err_fd > 0)
			close(err_fd);
		return hdr_err;
	}

	if (si->nr_ours || si->nr_theirs) {
		alt_shallow_file = setup_temporary_shallow(si->shallow);
		argv_array_push(&child.args, "--shallow-file");
		argv_array_push(&child.args, alt_shallow_file);
	}

	tmp_objdir = tmp_objdir_create();
	if (!tmp_objdir) {
		if (err_fd > 0)
			close(err_fd);
		return "unable to create temporary object directory";
	}
	child.env = tmp_objdir_env(tmp_objdir);

	/*
	 * Normally we just pass the tmp_objdir environment to the child
	 * processes that do the heavy lifting, but we may need to see these
	 * objects ourselves to set up shallow information.
	 */
	tmp_objdir_add_as_alternate(tmp_objdir);

	if (ntohl(hdr.hdr_entries) < unpack_limit) {
		argv_array_push(&child.args, "unpack-objects");
		push_header_arg(&child.args, &hdr);
		if (quiet)
			argv_array_push(&child.args, "-q");
		if (fsck_objects)
			argv_array_pushf(&child.args, "--strict%s",
				fsck_msg_types.buf);
		if (max_input_size)
			argv_array_pushf(&child.args, "--max-input-size=%"PRIuMAX,
				(uintmax_t)max_input_size);
		child.no_stdout = 1;
		child.err = err_fd;
		child.git_cmd = 1;
		status = run_command(&child);
		if (status)
			return "unpack-objects abnormal exit";
	} else {
		char hostname[HOST_NAME_MAX + 1];

		argv_array_pushl(&child.args, "index-pack", "--stdin", NULL);
		push_header_arg(&child.args, &hdr);

		if (xgethostname(hostname, sizeof(hostname)))
			xsnprintf(hostname, sizeof(hostname), "localhost");
		argv_array_pushf(&child.args,
				 "--keep=receive-pack %"PRIuMAX" on %s",
				 (uintmax_t)getpid(),
				 hostname);

		if (!quiet && err_fd)
			argv_array_push(&child.args, "--show-resolving-progress");
		if (use_sideband)
			argv_array_push(&child.args, "--report-end-of-input");
		if (fsck_objects)
			argv_array_pushf(&child.args, "--strict%s",
				fsck_msg_types.buf);
		if (!reject_thin)
			argv_array_push(&child.args, "--fix-thin");
		if (max_input_size)
			argv_array_pushf(&child.args, "--max-input-size=%"PRIuMAX,
				(uintmax_t)max_input_size);
		child.out = -1;
		child.err = err_fd;
		child.git_cmd = 1;
		status = start_command(&child);
		if (status)
			return "index-pack fork failed";
		pack_lockfile = index_pack_lockfile(child.out);
		close(child.out);
		status = finish_command(&child);
		if (status)
			return "index-pack abnormal exit";
		reprepare_packed_git(the_repository);
	}
	return NULL;
}

static const char *unpack_with_sideband(struct shallow_info *si)
{
	struct async muxer;
	const char *ret;

	if (!use_sideband)
		return unpack(0, si);

	use_keepalive = KEEPALIVE_AFTER_NUL;
	memset(&muxer, 0, sizeof(muxer));
	muxer.proc = copy_to_sideband;
	muxer.in = -1;
	if (start_async(&muxer))
		return NULL;

	ret = unpack(muxer.in, si);

	finish_async(&muxer);
	return ret;
}

static void prepare_shallow_update(struct shallow_info *si)
{
	int i, j, k, bitmap_size = DIV_ROUND_UP(si->ref->nr, 32);

	ALLOC_ARRAY(si->used_shallow, si->shallow->nr);
	assign_shallow_commits_to_refs(si, si->used_shallow, NULL);

	si->need_reachability_test =
		xcalloc(si->shallow->nr, sizeof(*si->need_reachability_test));
	si->reachable =
		xcalloc(si->shallow->nr, sizeof(*si->reachable));
	si->shallow_ref = xcalloc(si->ref->nr, sizeof(*si->shallow_ref));

	for (i = 0; i < si->nr_ours; i++)
		si->need_reachability_test[si->ours[i]] = 1;

	for (i = 0; i < si->shallow->nr; i++) {
		if (!si->used_shallow[i])
			continue;
		for (j = 0; j < bitmap_size; j++) {
			if (!si->used_shallow[i][j])
				continue;
			si->need_reachability_test[i]++;
			for (k = 0; k < 32; k++)
				if (si->used_shallow[i][j] & (1U << k))
					si->shallow_ref[j * 32 + k]++;
		}

		/*
		 * true for those associated with some refs and belong
		 * in "ours" list aka "step 7 not done yet"
		 */
		si->need_reachability_test[i] =
			si->need_reachability_test[i] > 1;
	}

	/*
	 * keep hooks happy by forcing a temporary shallow file via
	 * env variable because we can't add --shallow-file to every
	 * command. check_connected() will be done with
	 * true .git/shallow though.
	 */
	setenv(GIT_SHALLOW_FILE_ENVIRONMENT, alt_shallow_file, 1);
}

static void update_shallow_info(struct command *commands,
				struct shallow_info *si,
				struct oid_array *ref)
{
	struct command *cmd;
	int *ref_status;
	remove_nonexistent_theirs_shallow(si);
	if (!si->nr_ours && !si->nr_theirs) {
		shallow_update = 0;
		return;
	}

	for (cmd = commands; cmd; cmd = cmd->next) {
		if (is_null_oid(&cmd->new_oid))
			continue;
		oid_array_append(ref, &cmd->new_oid);
		cmd->index = ref->nr - 1;
	}
	si->ref = ref;

	if (shallow_update) {
		prepare_shallow_update(si);
		return;
	}

	ALLOC_ARRAY(ref_status, ref->nr);
	assign_shallow_commits_to_refs(si, NULL, ref_status);
	for (cmd = commands; cmd; cmd = cmd->next) {
		if (is_null_oid(&cmd->new_oid))
			continue;
		if (ref_status[cmd->index]) {
			cmd->error_string = "shallow update not allowed";
			cmd->skip_update = 1;
		}
	}
	free(ref_status);
}

static void report(struct command *commands, const char *unpack_status)
{
	struct command *cmd;
	struct strbuf buf = STRBUF_INIT;

	packet_buf_write(&buf, "unpack %s\n",
			 unpack_status ? unpack_status : "ok");
	for (cmd = commands; cmd; cmd = cmd->next) {
		if (!cmd->error_string)
			packet_buf_write(&buf, "ok %s\n",
					 cmd->ref_name);
		else
			packet_buf_write(&buf, "ng %s %s\n",
					 cmd->ref_name, cmd->error_string);
	}
	packet_buf_flush(&buf);

	if (use_sideband)
		send_sideband(1, 1, buf.buf, buf.len, use_sideband);
	else
		write_or_die(1, buf.buf, buf.len);
	strbuf_release(&buf);
}

static int delete_only(struct command *commands)
{
	struct command *cmd;
	for (cmd = commands; cmd; cmd = cmd->next) {
		if (!is_null_oid(&cmd->new_oid))
			return 0;
	}
	return 1;
}

int cmd_receive_pack(int argc, const char **argv, const char *prefix)
{
	int advertise_refs = 0;
	struct command *commands;
	struct oid_array shallow = OID_ARRAY_INIT;
	struct oid_array ref = OID_ARRAY_INIT;
	struct shallow_info si;
	struct packet_reader reader;

	struct option options[] = {
		OPT__QUIET(&quiet, N_("quiet")),
		OPT_HIDDEN_BOOL(0, "stateless-rpc", &stateless_rpc, NULL),
		OPT_HIDDEN_BOOL(0, "advertise-refs", &advertise_refs, NULL),
		OPT_HIDDEN_BOOL(0, "reject-thin-pack-for-testing", &reject_thin, NULL),
		OPT_END()
	};

	packet_trace_identity("receive-pack");

	argc = parse_options(argc, argv, prefix, options, receive_pack_usage, 0);

	if (argc > 1)
		usage_msg_opt(_("Too many arguments."), receive_pack_usage, options);
	if (argc == 0)
		usage_msg_opt(_("You must specify a directory."), receive_pack_usage, options);

	service_dir = argv[0];

	setup_path();

	if (!enter_repo(service_dir, 0))
		die("'%s' does not appear to be a git repository", service_dir);

	git_config(receive_pack_config, NULL);
	if (cert_nonce_seed)
		push_cert_nonce = prepare_push_cert_nonce(service_dir, time(NULL));

	if (0 <= transfer_unpack_limit)
		unpack_limit = transfer_unpack_limit;
	else if (0 <= receive_unpack_limit)
		unpack_limit = receive_unpack_limit;

	switch (determine_protocol_version_server()) {
	case protocol_v2:
		/*
		 * push support for protocol v2 has not been implemented yet,
		 * so ignore the request to use v2 and fallback to using v0.
		 */
		break;
	case protocol_v1:
		/*
		 * v1 is just the original protocol with a version string,
		 * so just fall through after writing the version string.
		 */
		if (advertise_refs || !stateless_rpc)
			packet_write_fmt(1, "version 1\n");

		/* fallthrough */
	case protocol_v0:
		break;
	case protocol_unknown_version:
		BUG("unknown protocol version");
	}

	if (advertise_refs || !stateless_rpc) {
		write_head_info();
	}
	if (advertise_refs)
		return 0;

	packet_reader_init(&reader, 0, NULL, 0,
			   PACKET_READ_CHOMP_NEWLINE |
			   PACKET_READ_DIE_ON_ERR_PACKET);

	if ((commands = read_head_info(&reader, &shallow)) != NULL) {
		const char *unpack_status = NULL;
		struct string_list push_options = STRING_LIST_INIT_DUP;

		if (use_push_options)
			read_push_options(&reader, &push_options);
		if (!check_cert_push_options(&push_options)) {
			struct command *cmd;
			for (cmd = commands; cmd; cmd = cmd->next)
				cmd->error_string = "inconsistent push options";
		}

		prepare_shallow_info(&si, &shallow);
		if (!si.nr_ours && !si.nr_theirs)
			shallow_update = 0;
		if (!delete_only(commands)) {
			unpack_status = unpack_with_sideband(&si);
			update_shallow_info(commands, &si, &ref);
		}
		use_keepalive = KEEPALIVE_ALWAYS;
		execute_commands(commands, unpack_status, &si,
				 &push_options);
		if (pack_lockfile)
			unlink_or_warn(pack_lockfile);
		if (report_status)
			report(commands, unpack_status);
		run_receive_hook(commands, "post-receive", 1,
				 &push_options);
		run_update_post_hook(commands);
		string_list_clear(&push_options, 0);
		if (auto_gc) {
			const char *argv_gc_auto[] = {
				"gc", "--auto", "--quiet", NULL,
			};
			struct child_process proc = CHILD_PROCESS_INIT;

			proc.no_stdin = 1;
			proc.stdout_to_stderr = 1;
			proc.err = use_sideband ? -1 : 0;
			proc.git_cmd = 1;
			proc.argv = argv_gc_auto;

			close_object_store(the_repository->objects);
			if (!start_command(&proc)) {
				if (use_sideband)
					copy_to_sideband(proc.err, -1, NULL);
				finish_command(&proc);
			}
		}
		if (auto_update_server_info)
			update_server_info(0);
		clear_shallow_info(&si);
	}
	if (use_sideband)
		packet_flush(1);
	oid_array_clear(&shallow);
	oid_array_clear(&ref);
	free((void *)push_cert_nonce);
	return 0;
}