archive-tar.c - jrn/git - Git at Google

 /*
  * Copyright (c) 2005, 2006 Rene Scharfe
  */
 #include "cache.h"
 #include "tar.h"
 #include "archive.h"
 #include "streaming.h"
 #include "run-command.h"

 #define RECORDSIZE	(512)
 #define BLOCKSIZE	(RECORDSIZE * 20)

 static char block[BLOCKSIZE];
 static unsigned long offset;

 static int tar_umask = 002;

 static int write_tar_filter_archive(const struct archiver *ar,
 				    struct archiver_args *args);

 /* writes out the whole block, but only if it is full */
 static void write_if_needed(void)
 {
 	if (offset == BLOCKSIZE) {
 		write_or_die(1, block, BLOCKSIZE);
 		offset = 0;
 	}
 }

 /*
  * queues up writes, so that all our write(2) calls write exactly one
  * full block; pads writes to RECORDSIZE
  */
 static void do_write_blocked(const void *data, unsigned long size)
 {
 	const char *buf = data;

 	if (offset) {
 		unsigned long chunk = BLOCKSIZE - offset;
 		if (size < chunk)
 			chunk = size;
 		memcpy(block + offset, buf, chunk);
 		size -= chunk;
 		offset += chunk;
 		buf += chunk;
 		write_if_needed();
 	}
 	while (size >= BLOCKSIZE) {
 		write_or_die(1, buf, BLOCKSIZE);
 		size -= BLOCKSIZE;
 		buf += BLOCKSIZE;
 	}
 	if (size) {
 		memcpy(block + offset, buf, size);
 		offset += size;
 	}
 }

 static void finish_record(void)
 {
 	unsigned long tail;
 	tail = offset % RECORDSIZE;
 	if (tail)  {
 		memset(block + offset, 0, RECORDSIZE - tail);
 		offset += RECORDSIZE - tail;
 	}
 	write_if_needed();
 }

 static void write_blocked(const void *data, unsigned long size)
 {
 	do_write_blocked(data, size);
 	finish_record();
 }

 /*
  * The end of tar archives is marked by 2*512 nul bytes and after that
  * follows the rest of the block (if any).
  */
 static void write_trailer(void)
 {
 	int tail = BLOCKSIZE - offset;
 	memset(block + offset, 0, tail);
 	write_or_die(1, block, BLOCKSIZE);
 	if (tail < 2 * RECORDSIZE) {
 		memset(block, 0, offset);
 		write_or_die(1, block, BLOCKSIZE);
 	}
 }

 /*
  * queues up writes, so that all our write(2) calls write exactly one
  * full block; pads writes to RECORDSIZE
  */
 static int stream_blocked(const unsigned char *sha1)
 {
 	struct git_istream *st;
 	enum object_type type;
 	unsigned long sz;
 	char buf[BLOCKSIZE];
 	ssize_t readlen;

 	st = open_istream(sha1, &type, &sz, NULL);
 	if (!st)
 		return error("cannot stream blob %s", sha1_to_hex(sha1));
 	for (;;) {
 		readlen = read_istream(st, buf, sizeof(buf));
 		if (readlen <= 0)
 			break;
 		do_write_blocked(buf, readlen);
 	}
 	close_istream(st);
 	if (!readlen)
 		finish_record();
 	return readlen;
 }

 /*
  * pax extended header records have the format "%u %s=%s\n".  %u contains
  * the size of the whole string (including the %u), the first %s is the
  * keyword, the second one is the value.  This function constructs such a
  * string and appends it to a struct strbuf.
  */
 static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
                                      const char *value, unsigned int valuelen)
 {
 	int len, tmp;

 	/* "%u %s=%s\n" */
 	len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
 	for (tmp = len; tmp > 9; tmp /= 10)
 		len++;

 	strbuf_grow(sb, len);
 	strbuf_addf(sb, "%u %s=", len, keyword);
 	strbuf_add(sb, value, valuelen);
 	strbuf_addch(sb, '\n');
 }

 static unsigned int ustar_header_chksum(const struct ustar_header *header)
 {
 	const unsigned char *p = (const unsigned char *)header;
 	unsigned int chksum = 0;
 	while (p < (const unsigned char *)header->chksum)
 		chksum += *p++;
 	chksum += sizeof(header->chksum) * ' ';
 	p += sizeof(header->chksum);
 	while (p < (const unsigned char *)header + sizeof(struct ustar_header))
 		chksum += *p++;
 	return chksum;
 }

 static size_t get_path_prefix(const char *path, size_t pathlen, size_t maxlen)
 {
 	size_t i = pathlen;
 	if (i > 1 && path[i - 1] == '/')
 		i--;
 	if (i > maxlen)
 		i = maxlen;
 	do {
 		i--;
 	} while (i > 0 && path[i] != '/');
 	return i;
 }

 static void prepare_header(struct archiver_args *args,
 			   struct ustar_header *header,
 			   unsigned int mode, unsigned long size)
 {
 	sprintf(header->mode, "%07o", mode & 07777);
 	sprintf(header->size, "%011lo", S_ISREG(mode) ? size : 0);
 	sprintf(header->mtime, "%011lo", (unsigned long) args->time);

 	sprintf(header->uid, "%07o", 0);
 	sprintf(header->gid, "%07o", 0);
 	strlcpy(header->uname, "root", sizeof(header->uname));
 	strlcpy(header->gname, "root", sizeof(header->gname));
 	sprintf(header->devmajor, "%07o", 0);
 	sprintf(header->devminor, "%07o", 0);

 	memcpy(header->magic, "ustar", 6);
 	memcpy(header->version, "00", 2);

 	sprintf(header->chksum, "%07o", ustar_header_chksum(header));
 }

 static int write_extended_header(struct archiver_args *args,
 				 const unsigned char *sha1,
 				 const void *buffer, unsigned long size)
 {
 	struct ustar_header header;
 	unsigned int mode;
 	memset(&header, 0, sizeof(header));
 	*header.typeflag = TYPEFLAG_EXT_HEADER;
 	mode = 0100666;
 	sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
 	prepare_header(args, &header, mode, size);
 	write_blocked(&header, sizeof(header));
 	write_blocked(buffer, size);
 	return 0;
 }

 static int write_tar_entry(struct archiver_args *args,
 			   const unsigned char *sha1,
 			   const char *path, size_t pathlen,
 			   unsigned int mode)
 {
 	struct ustar_header header;
 	struct strbuf ext_header = STRBUF_INIT;
 	unsigned int old_mode = mode;
 	unsigned long size;
 	void *buffer;
 	int err = 0;

 	memset(&header, 0, sizeof(header));

 	if (S_ISDIR(mode) || S_ISGITLINK(mode)) {
 		*header.typeflag = TYPEFLAG_DIR;
 		mode = (mode | 0777) & ~tar_umask;
 	} else if (S_ISLNK(mode)) {
 		*header.typeflag = TYPEFLAG_LNK;
 		mode |= 0777;
 	} else if (S_ISREG(mode)) {
 		*header.typeflag = TYPEFLAG_REG;
 		mode = (mode | ((mode & 0100) ? 0777 : 0666)) & ~tar_umask;
 	} else {
 		return error("unsupported file mode: 0%o (SHA1: %s)",
 			     mode, sha1_to_hex(sha1));
 	}
 	if (pathlen > sizeof(header.name)) {
 		size_t plen = get_path_prefix(path, pathlen,
 					      sizeof(header.prefix));
 		size_t rest = pathlen - plen - 1;
 		if (plen > 0 && rest <= sizeof(header.name)) {
 			memcpy(header.prefix, path, plen);
 				memcpy(header.name, path + plen + 1, rest);
 		} else {
 			sprintf(header.name, "%s.data",
 				sha1_to_hex(sha1));
 			strbuf_append_ext_header(&ext_header, "path",
 						 path, pathlen);
 		}
 	} else
 		memcpy(header.name, path, pathlen);

 	if (S_ISREG(mode) && !args->convert &&
 	    sha1_object_info(sha1, &size) == OBJ_BLOB &&
 	    size > big_file_threshold)
 		buffer = NULL;
 	else if (S_ISLNK(mode) || S_ISREG(mode)) {
 		enum object_type type;
 		buffer = sha1_file_to_archive(args, path, sha1, old_mode, &type, &size);
 		if (!buffer)
 			return error("cannot read %s", sha1_to_hex(sha1));
 	} else {
 		buffer = NULL;
 		size = 0;
 	}

 	if (S_ISLNK(mode)) {
 		if (size > sizeof(header.linkname)) {
 			sprintf(header.linkname, "see %s.paxheader",
 			        sha1_to_hex(sha1));
 			strbuf_append_ext_header(&ext_header, "linkpath",
 			                         buffer, size);
 		} else
 			memcpy(header.linkname, buffer, size);
 	}

 	prepare_header(args, &header, mode, size);

 	if (ext_header.len > 0) {
 		err = write_extended_header(args, sha1, ext_header.buf,
 					    ext_header.len);
 		if (err) {
 			free(buffer);
 			return err;
 		}
 	}
 	strbuf_release(&ext_header);
 	write_blocked(&header, sizeof(header));
 	if (S_ISREG(mode) && size > 0) {
 		if (buffer)
 			write_blocked(buffer, size);
 		else
 			err = stream_blocked(sha1);
 	}
 	free(buffer);
 	return err;
 }

 static int write_global_extended_header(struct archiver_args *args)
 {
 	const unsigned char *sha1 = args->commit_sha1;
 	struct strbuf ext_header = STRBUF_INIT;
 	struct ustar_header header;
 	unsigned int mode;
 	int err = 0;

 	strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
 	memset(&header, 0, sizeof(header));
 	*header.typeflag = TYPEFLAG_GLOBAL_HEADER;
 	mode = 0100666;
 	strcpy(header.name, "pax_global_header");
 	prepare_header(args, &header, mode, ext_header.len);
 	write_blocked(&header, sizeof(header));
 	write_blocked(ext_header.buf, ext_header.len);
 	strbuf_release(&ext_header);
 	return err;
 }

 static struct archiver **tar_filters;
 static int nr_tar_filters;
 static int alloc_tar_filters;

 static struct archiver *find_tar_filter(const char *name, int len)
 {
 	int i;
 	for (i = 0; i < nr_tar_filters; i++) {
 		struct archiver *ar = tar_filters[i];
 		if (!strncmp(ar->name, name, len) && !ar->name[len])
 			return ar;
 	}
 	return NULL;
 }

 static int tar_filter_config(const char *var, const char *value, void *data)
 {
 	struct archiver *ar;
 	const char *name;
 	const char *type;
 	int namelen;

 	if (parse_config_key(var, "tar", &name, &namelen, &type) < 0 || !name)
 		return 0;

 	ar = find_tar_filter(name, namelen);
 	if (!ar) {
 		ar = xcalloc(1, sizeof(*ar));
 		ar->name = xmemdupz(name, namelen);
 		ar->write_archive = write_tar_filter_archive;
 		ar->flags = ARCHIVER_WANT_COMPRESSION_LEVELS;
 		ALLOC_GROW(tar_filters, nr_tar_filters + 1, alloc_tar_filters);
 		tar_filters[nr_tar_filters++] = ar;
 	}

 	if (!strcmp(type, "command")) {
 		if (!value)
 			return config_error_nonbool(var);
 		free(ar->data);
 		ar->data = xstrdup(value);
 		return 0;
 	}
 	if (!strcmp(type, "remote")) {
 		if (git_config_bool(var, value))
 			ar->flags |= ARCHIVER_REMOTE;
 		else
 			ar->flags &= ~ARCHIVER_REMOTE;
 		return 0;
 	}

 	return 0;
 }

 static int git_tar_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "tar.umask")) {
 		if (value && !strcmp(value, "user")) {
 			tar_umask = umask(0);
 			umask(tar_umask);
 		} else {
 			tar_umask = git_config_int(var, value);
 		}
 		return 0;
 	}

 	return tar_filter_config(var, value, cb);
 }

 static int write_tar_archive(const struct archiver *ar,
 			     struct archiver_args *args)
 {
 	int err = 0;

 	if (args->commit_sha1)
 		err = write_global_extended_header(args);
 	if (!err)
 		err = write_archive_entries(args, write_tar_entry);
 	if (!err)
 		write_trailer();
 	return err;
 }

 static int write_tar_filter_archive(const struct archiver *ar,
 				    struct archiver_args *args)
 {
 	struct strbuf cmd = STRBUF_INIT;
 	struct child_process filter;
 	const char *argv[2];
 	int r;

 	if (!ar->data)
 		die("BUG: tar-filter archiver called with no filter defined");

 	strbuf_addstr(&cmd, ar->data);
 	if (args->compression_level >= 0)
 		strbuf_addf(&cmd, " -%d", args->compression_level);

 	memset(&filter, 0, sizeof(filter));
 	argv[0] = cmd.buf;
 	argv[1] = NULL;
 	filter.argv = argv;
 	filter.use_shell = 1;
 	filter.in = -1;

 	if (start_command(&filter) < 0)
 		die_errno("unable to start '%s' filter", argv[0]);
 	close(1);
 	if (dup2(filter.in, 1) < 0)
 		die_errno("unable to redirect descriptor");
 	close(filter.in);

 	r = write_tar_archive(ar, args);

 	close(1);
 	if (finish_command(&filter) != 0)
 		die("'%s' filter reported error", argv[0]);

 	strbuf_release(&cmd);
 	return r;
 }

 static struct archiver tar_archiver = {
 	"tar",
 	write_tar_archive,
 	ARCHIVER_REMOTE
 };

 void init_tar_archiver(void)
 {
 	int i;
 	register_archiver(&tar_archiver);

 	tar_filter_config("tar.tgz.command", "gzip -cn", NULL);
 	tar_filter_config("tar.tgz.remote", "true", NULL);
 	tar_filter_config("tar.tar.gz.command", "gzip -cn", NULL);
 	tar_filter_config("tar.tar.gz.remote", "true", NULL);
 	git_config(git_tar_config, NULL);
 	for (i = 0; i < nr_tar_filters; i++) {
 		/* omit any filters that never had a command configured */
 		if (tar_filters[i]->data)
 			register_archiver(tar_filters[i]);
 	}
 }
	/*
	* Copyright (c) 2005, 2006 Rene Scharfe
	*/
	#include "cache.h"
	#include "tar.h"
	#include "archive.h"
	#include "streaming.h"
	#include "run-command.h"

	#define RECORDSIZE (512)
	#define BLOCKSIZE (RECORDSIZE * 20)

	static char block[BLOCKSIZE];
	static unsigned long offset;

	static int tar_umask = 002;

	static int write_tar_filter_archive(const struct archiver *ar,
	struct archiver_args *args);

	/* writes out the whole block, but only if it is full */
	static void write_if_needed(void)
	{
	if (offset == BLOCKSIZE) {
	write_or_die(1, block, BLOCKSIZE);
	offset = 0;
	}
	}

	/*
	* queues up writes, so that all our write(2) calls write exactly one
	* full block; pads writes to RECORDSIZE
	*/
	static void do_write_blocked(const void *data, unsigned long size)
	{
	const char *buf = data;

	if (offset) {
	unsigned long chunk = BLOCKSIZE - offset;
	if (size < chunk)
	chunk = size;
	memcpy(block + offset, buf, chunk);
	size -= chunk;
	offset += chunk;
	buf += chunk;
	write_if_needed();
	}
	while (size >= BLOCKSIZE) {
	write_or_die(1, buf, BLOCKSIZE);
	size -= BLOCKSIZE;
	buf += BLOCKSIZE;
	}
	if (size) {
	memcpy(block + offset, buf, size);
	offset += size;
	}
	}

	static void finish_record(void)
	{
	unsigned long tail;
	tail = offset % RECORDSIZE;
	if (tail) {
	memset(block + offset, 0, RECORDSIZE - tail);
	offset += RECORDSIZE - tail;
	}
	write_if_needed();
	}

	static void write_blocked(const void *data, unsigned long size)
	{
	do_write_blocked(data, size);
	finish_record();
	}

	/*
	* The end of tar archives is marked by 2*512 nul bytes and after that
	* follows the rest of the block (if any).
	*/
	static void write_trailer(void)
	{
	int tail = BLOCKSIZE - offset;
	memset(block + offset, 0, tail);
	write_or_die(1, block, BLOCKSIZE);
	if (tail < 2 * RECORDSIZE) {
	memset(block, 0, offset);
	write_or_die(1, block, BLOCKSIZE);
	}
	}

	/*
	* queues up writes, so that all our write(2) calls write exactly one
	* full block; pads writes to RECORDSIZE
	*/
	static int stream_blocked(const unsigned char *sha1)
	{
	struct git_istream *st;
	enum object_type type;
	unsigned long sz;
	char buf[BLOCKSIZE];
	ssize_t readlen;

	st = open_istream(sha1, &type, &sz, NULL);
	if (!st)
	return error("cannot stream blob %s", sha1_to_hex(sha1));
	for (;;) {
	readlen = read_istream(st, buf, sizeof(buf));
	if (readlen <= 0)
	break;
	do_write_blocked(buf, readlen);
	}
	close_istream(st);
	if (!readlen)
	finish_record();
	return readlen;
	}

	/*
	* pax extended header records have the format "%u %s=%s\n". %u contains
	* the size of the whole string (including the %u), the first %s is the
	* keyword, the second one is the value. This function constructs such a
	* string and appends it to a struct strbuf.
	*/
	static void strbuf_append_ext_header(struct strbuf sb, const char keyword,
	const char *value, unsigned int valuelen)
	{
	int len, tmp;

	/* "%u %s=%s\n" */
	len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
	for (tmp = len; tmp > 9; tmp /= 10)
	len++;

	strbuf_grow(sb, len);
	strbuf_addf(sb, "%u %s=", len, keyword);
	strbuf_add(sb, value, valuelen);
	strbuf_addch(sb, '\n');
	}

	static unsigned int ustar_header_chksum(const struct ustar_header *header)
	{
	const unsigned char p = (const unsigned char )header;
	unsigned int chksum = 0;
	while (p < (const unsigned char *)header->chksum)
	chksum += *p++;
	chksum += sizeof(header->chksum) * ' ';
	p += sizeof(header->chksum);
	while (p < (const unsigned char *)header + sizeof(struct ustar_header))
	chksum += *p++;
	return chksum;
	}

	static size_t get_path_prefix(const char *path, size_t pathlen, size_t maxlen)
	{
	size_t i = pathlen;
	if (i > 1 && path[i - 1] == '/')
	i--;
	if (i > maxlen)
	i = maxlen;
	do {
	i--;
	} while (i > 0 && path[i] != '/');
	return i;
	}

	static void prepare_header(struct archiver_args *args,
	struct ustar_header *header,
	unsigned int mode, unsigned long size)
	{
	sprintf(header->mode, "%07o", mode & 07777);
	sprintf(header->size, "%011lo", S_ISREG(mode) ? size : 0);
	sprintf(header->mtime, "%011lo", (unsigned long) args->time);

	sprintf(header->uid, "%07o", 0);
	sprintf(header->gid, "%07o", 0);
	strlcpy(header->uname, "root", sizeof(header->uname));
	strlcpy(header->gname, "root", sizeof(header->gname));
	sprintf(header->devmajor, "%07o", 0);
	sprintf(header->devminor, "%07o", 0);

	memcpy(header->magic, "ustar", 6);
	memcpy(header->version, "00", 2);

	sprintf(header->chksum, "%07o", ustar_header_chksum(header));
	}

	static int write_extended_header(struct archiver_args *args,
	const unsigned char *sha1,
	const void *buffer, unsigned long size)
	{
	struct ustar_header header;
	unsigned int mode;
	memset(&header, 0, sizeof(header));
	*header.typeflag = TYPEFLAG_EXT_HEADER;
	mode = 0100666;
	sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
	prepare_header(args, &header, mode, size);
	write_blocked(&header, sizeof(header));
	write_blocked(buffer, size);
	return 0;
	}

	static int write_tar_entry(struct archiver_args *args,
	const unsigned char *sha1,
	const char *path, size_t pathlen,
	unsigned int mode)
	{
	struct ustar_header header;
	struct strbuf ext_header = STRBUF_INIT;
	unsigned int old_mode = mode;
	unsigned long size;
	void *buffer;
	int err = 0;

	memset(&header, 0, sizeof(header));

	if (S_ISDIR(mode) \|\| S_ISGITLINK(mode)) {
	*header.typeflag = TYPEFLAG_DIR;
	mode = (mode \| 0777) & ~tar_umask;
	} else if (S_ISLNK(mode)) {
	*header.typeflag = TYPEFLAG_LNK;
	mode \|= 0777;
	} else if (S_ISREG(mode)) {
	*header.typeflag = TYPEFLAG_REG;
	mode = (mode \| ((mode & 0100) ? 0777 : 0666)) & ~tar_umask;
	} else {
	return error("unsupported file mode: 0%o (SHA1: %s)",
	mode, sha1_to_hex(sha1));
	}
	if (pathlen > sizeof(header.name)) {
	size_t plen = get_path_prefix(path, pathlen,
	sizeof(header.prefix));
	size_t rest = pathlen - plen - 1;
	if (plen > 0 && rest <= sizeof(header.name)) {
	memcpy(header.prefix, path, plen);
	memcpy(header.name, path + plen + 1, rest);
	} else {
	sprintf(header.name, "%s.data",
	sha1_to_hex(sha1));
	strbuf_append_ext_header(&ext_header, "path",
	path, pathlen);
	}
	} else
	memcpy(header.name, path, pathlen);

	if (S_ISREG(mode) && !args->convert &&
	sha1_object_info(sha1, &size) == OBJ_BLOB &&
	size > big_file_threshold)
	buffer = NULL;
	else if (S_ISLNK(mode) \|\| S_ISREG(mode)) {
	enum object_type type;
	buffer = sha1_file_to_archive(args, path, sha1, old_mode, &type, &size);
	if (!buffer)
	return error("cannot read %s", sha1_to_hex(sha1));
	} else {
	buffer = NULL;
	size = 0;
	}

	if (S_ISLNK(mode)) {
	if (size > sizeof(header.linkname)) {
	sprintf(header.linkname, "see %s.paxheader",
	sha1_to_hex(sha1));
	strbuf_append_ext_header(&ext_header, "linkpath",
	buffer, size);
	} else
	memcpy(header.linkname, buffer, size);
	}

	prepare_header(args, &header, mode, size);

	if (ext_header.len > 0) {
	err = write_extended_header(args, sha1, ext_header.buf,
	ext_header.len);
	if (err) {
	free(buffer);
	return err;
	}
	}
	strbuf_release(&ext_header);
	write_blocked(&header, sizeof(header));
	if (S_ISREG(mode) && size > 0) {
	if (buffer)
	write_blocked(buffer, size);
	else
	err = stream_blocked(sha1);
	}
	free(buffer);
	return err;
	}

	static int write_global_extended_header(struct archiver_args *args)
	{
	const unsigned char *sha1 = args->commit_sha1;
	struct strbuf ext_header = STRBUF_INIT;
	struct ustar_header header;
	unsigned int mode;
	int err = 0;

	strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
	memset(&header, 0, sizeof(header));
	*header.typeflag = TYPEFLAG_GLOBAL_HEADER;
	mode = 0100666;
	strcpy(header.name, "pax_global_header");
	prepare_header(args, &header, mode, ext_header.len);
	write_blocked(&header, sizeof(header));
	write_blocked(ext_header.buf, ext_header.len);
	strbuf_release(&ext_header);
	return err;
	}

	static struct archiver **tar_filters;
	static int nr_tar_filters;
	static int alloc_tar_filters;

	static struct archiver find_tar_filter(const char name, int len)
	{
	int i;
	for (i = 0; i < nr_tar_filters; i++) {
	struct archiver *ar = tar_filters[i];
	if (!strncmp(ar->name, name, len) && !ar->name[len])
	return ar;
	}
	return NULL;
	}

	static int tar_filter_config(const char var, const char value, void *data)
	{
	struct archiver *ar;
	const char *name;
	const char *type;
	int namelen;

	if (parse_config_key(var, "tar", &name, &namelen, &type) < 0 \|\| !name)
	return 0;

	ar = find_tar_filter(name, namelen);
	if (!ar) {
	ar = xcalloc(1, sizeof(*ar));
	ar->name = xmemdupz(name, namelen);
	ar->write_archive = write_tar_filter_archive;
	ar->flags = ARCHIVER_WANT_COMPRESSION_LEVELS;
	ALLOC_GROW(tar_filters, nr_tar_filters + 1, alloc_tar_filters);
	tar_filters[nr_tar_filters++] = ar;
	}

	if (!strcmp(type, "command")) {
	if (!value)
	return config_error_nonbool(var);
	free(ar->data);
	ar->data = xstrdup(value);
	return 0;
	}
	if (!strcmp(type, "remote")) {
	if (git_config_bool(var, value))
	ar->flags \|= ARCHIVER_REMOTE;
	else
	ar->flags &= ~ARCHIVER_REMOTE;
	return 0;
	}

	return 0;
	}

	static int git_tar_config(const char var, const char value, void *cb)
	{
	if (!strcmp(var, "tar.umask")) {
	if (value && !strcmp(value, "user")) {
	tar_umask = umask(0);
	umask(tar_umask);
	} else {
	tar_umask = git_config_int(var, value);
	}
	return 0;
	}

	return tar_filter_config(var, value, cb);
	}

	static int write_tar_archive(const struct archiver *ar,
	struct archiver_args *args)
	{
	int err = 0;

	if (args->commit_sha1)
	err = write_global_extended_header(args);
	if (!err)
	err = write_archive_entries(args, write_tar_entry);
	if (!err)
	write_trailer();
	return err;
	}

	static int write_tar_filter_archive(const struct archiver *ar,
	struct archiver_args *args)
	{
	struct strbuf cmd = STRBUF_INIT;
	struct child_process filter;
	const char *argv[2];
	int r;

	if (!ar->data)
	die("BUG: tar-filter archiver called with no filter defined");

	strbuf_addstr(&cmd, ar->data);
	if (args->compression_level >= 0)
	strbuf_addf(&cmd, " -%d", args->compression_level);

	memset(&filter, 0, sizeof(filter));
	argv[0] = cmd.buf;
	argv[1] = NULL;
	filter.argv = argv;
	filter.use_shell = 1;
	filter.in = -1;

	if (start_command(&filter) < 0)
	die_errno("unable to start '%s' filter", argv[0]);
	close(1);
	if (dup2(filter.in, 1) < 0)
	die_errno("unable to redirect descriptor");
	close(filter.in);

	r = write_tar_archive(ar, args);

	close(1);
	if (finish_command(&filter) != 0)
	die("'%s' filter reported error", argv[0]);

	strbuf_release(&cmd);
	return r;
	}

	static struct archiver tar_archiver = {
	"tar",
	write_tar_archive,
	ARCHIVER_REMOTE
	};

	void init_tar_archiver(void)
	{
	int i;
	register_archiver(&tar_archiver);

	tar_filter_config("tar.tgz.command", "gzip -cn", NULL);
	tar_filter_config("tar.tgz.remote", "true", NULL);
	tar_filter_config("tar.tar.gz.command", "gzip -cn", NULL);
	tar_filter_config("tar.tar.gz.remote", "true", NULL);
	git_config(git_tar_config, NULL);
	for (i = 0; i < nr_tar_filters; i++) {
	/* omit any filters that never had a command configured */
	if (tar_filters[i]->data)
	register_archiver(tar_filters[i]);
	}
	}