convert.c - git - Git at Google

 #include "cache.h"
 #include "attr.h"
 #include "run-command.h"

 /*
  * convert.c - convert a file when checking it out and checking it in.
  *
  * This should use the pathname to decide on whether it wants to do some
  * more interesting conversions (automatic gzip/unzip, general format
  * conversions etc etc), but by default it just does automatic CRLF<->LF
  * translation when the "auto_crlf" option is set.
  */

 #define CRLF_GUESS	(-1)
 #define CRLF_BINARY	0
 #define CRLF_TEXT	1
 #define CRLF_INPUT	2

 struct text_stat {
 	/* CR, LF and CRLF counts */
 	unsigned cr, lf, crlf;

 	/* These are just approximations! */
 	unsigned printable, nonprintable;
 };

 static void gather_stats(const char *buf, unsigned long size, struct text_stat *stats)
 {
 	unsigned long i;

 	memset(stats, 0, sizeof(*stats));

 	for (i = 0; i < size; i++) {
 		unsigned char c = buf[i];
 		if (c == '\r') {
 			stats->cr++;
 			if (i+1 < size && buf[i+1] == '\n')
 				stats->crlf++;
 			continue;
 		}
 		if (c == '\n') {
 			stats->lf++;
 			continue;
 		}
 		if (c == 127)
 			/* DEL */
 			stats->nonprintable++;
 		else if (c < 32) {
 			switch (c) {
 				/* BS, HT, ESC and FF */
 			case '\b': case '\t': case '\033': case '\014':
 				stats->printable++;
 				break;
 			default:
 				stats->nonprintable++;
 			}
 		}
 		else
 			stats->printable++;
 	}
 }

 /*
  * The same heuristics as diff.c::mmfile_is_binary()
  */
 static int is_binary(unsigned long size, struct text_stat *stats)
 {

 	if ((stats->printable >> 7) < stats->nonprintable)
 		return 1;
 	/*
 	 * Other heuristics? Average line length might be relevant,
 	 * as might LF vs CR vs CRLF counts..
 	 *
 	 * NOTE! It might be normal to have a low ratio of CRLF to LF
 	 * (somebody starts with a LF-only file and edits it with an editor
 	 * that adds CRLF only to lines that are added..). But do  we
 	 * want to support CR-only? Probably not.
 	 */
 	return 0;
 }

 static char *crlf_to_git(const char *path, const char *src, unsigned long *sizep, int action)
 {
 	char *buffer, *dst;
 	unsigned long size, nsize;
 	struct text_stat stats;

 	if ((action == CRLF_BINARY) || !auto_crlf)
 		return NULL;

 	size = *sizep;
 	if (!size)
 		return NULL;

 	gather_stats(src, size, &stats);

 	/* No CR? Nothing to convert, regardless. */
 	if (!stats.cr)
 		return NULL;

 	if (action == CRLF_GUESS) {
 		/*
 		 * We're currently not going to even try to convert stuff
 		 * that has bare CR characters. Does anybody do that crazy
 		 * stuff?
 		 */
 		if (stats.cr != stats.crlf)
 			return NULL;

 		/*
 		 * And add some heuristics for binary vs text, of course...
 		 */
 		if (is_binary(size, &stats))
 			return NULL;
 	}

 	/*
 	 * Ok, allocate a new buffer, fill it in, and return it
 	 * to let the caller know that we switched buffers.
 	 */
 	nsize = size - stats.crlf;
 	buffer = xmalloc(nsize);
 	*sizep = nsize;

 	dst = buffer;
 	if (action == CRLF_GUESS) {
 		/*
 		 * If we guessed, we already know we rejected a file with
 		 * lone CR, and we can strip a CR without looking at what
 		 * follow it.
 		 */
 		do {
 			unsigned char c = *src++;
 			if (c != '\r')
 				*dst++ = c;
 		} while (--size);
 	} else {
 		do {
 			unsigned char c = *src++;
 			if (! (c == '\r' && (1 < size && *src == '\n')))
 				*dst++ = c;
 		} while (--size);
 	}

 	return buffer;
 }

 static char *crlf_to_worktree(const char *path, const char *src, unsigned long *sizep, int action)
 {
 	char *buffer, *dst;
 	unsigned long size, nsize;
 	struct text_stat stats;
 	unsigned char last;

 	if ((action == CRLF_BINARY) || (action == CRLF_INPUT) ||
 	    auto_crlf <= 0)
 		return NULL;

 	size = *sizep;
 	if (!size)
 		return NULL;

 	gather_stats(src, size, &stats);

 	/* No LF? Nothing to convert, regardless. */
 	if (!stats.lf)
 		return NULL;

 	/* Was it already in CRLF format? */
 	if (stats.lf == stats.crlf)
 		return NULL;

 	if (action == CRLF_GUESS) {
 		/* If we have any bare CR characters, we're not going to touch it */
 		if (stats.cr != stats.crlf)
 			return NULL;

 		if (is_binary(size, &stats))
 			return NULL;
 	}

 	/*
 	 * Ok, allocate a new buffer, fill it in, and return it
 	 * to let the caller know that we switched buffers.
 	 */
 	nsize = size + stats.lf - stats.crlf;
 	buffer = xmalloc(nsize);
 	*sizep = nsize;
 	last = 0;

 	dst = buffer;
 	do {
 		unsigned char c = *src++;
 		if (c == '\n' && last != '\r')
 			*dst++ = '\r';
 		*dst++ = c;
 		last = c;
 	} while (--size);

 	return buffer;
 }

 static int filter_buffer(const char *path, const char *src,
 			 unsigned long size, const char *cmd)
 {
 	/*
 	 * Spawn cmd and feed the buffer contents through its stdin.
 	 */
 	struct child_process child_process;
 	int pipe_feed[2];
 	int write_err, status;

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

 	if (pipe(pipe_feed) < 0) {
 		error("cannot create pipe to run external filter %s", cmd);
 		return 1;
 	}

 	child_process.pid = fork();
 	if (child_process.pid < 0) {
 		error("cannot fork to run external filter %s", cmd);
 		close(pipe_feed[0]);
 		close(pipe_feed[1]);
 		return 1;
 	}
 	if (!child_process.pid) {
 		dup2(pipe_feed[0], 0);
 		close(pipe_feed[0]);
 		close(pipe_feed[1]);
 		execlp("sh", "sh", "-c", cmd, NULL);
 		return 1;
 	}
 	close(pipe_feed[0]);

 	write_err = (write_in_full(pipe_feed[1], src, size) < 0);
 	if (close(pipe_feed[1]))
 		write_err = 1;
 	if (write_err)
 		error("cannot feed the input to external filter %s", cmd);

 	status = finish_command(&child_process);
 	if (status)
 		error("external filter %s failed %d", cmd, -status);
 	return (write_err || status);
 }

 static char *apply_filter(const char *path, const char *src,
 			  unsigned long *sizep, const char *cmd)
 {
 	/*
 	 * Create a pipeline to have the command filter the buffer's
 	 * contents.
 	 *
 	 * (child --> cmd) --> us
 	 */
 	const int SLOP = 4096;
 	int pipe_feed[2];
 	int status;
 	char *dst;
 	unsigned long dstsize, dstalloc;
 	struct child_process child_process;

 	if (!cmd)
 		return NULL;

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

 	if (pipe(pipe_feed) < 0) {
 		error("cannot create pipe to run external filter %s", cmd);
 		return NULL;
 	}

 	fflush(NULL);
 	child_process.pid = fork();
 	if (child_process.pid < 0) {
 		error("cannot fork to run external filter %s", cmd);
 		close(pipe_feed[0]);
 		close(pipe_feed[1]);
 		return NULL;
 	}
 	if (!child_process.pid) {
 		dup2(pipe_feed[1], 1);
 		close(pipe_feed[0]);
 		close(pipe_feed[1]);
 		exit(filter_buffer(path, src, *sizep, cmd));
 	}
 	close(pipe_feed[1]);

 	dstalloc = *sizep;
 	dst = xmalloc(dstalloc);
 	dstsize = 0;

 	while (1) {
 		ssize_t numread = xread(pipe_feed[0], dst + dstsize,
 					dstalloc - dstsize);

 		if (numread <= 0) {
 			if (!numread)
 				break;
 			error("read from external filter %s failed", cmd);
 			free(dst);
 			dst = NULL;
 			break;
 		}
 		dstsize += numread;
 		if (dstalloc <= dstsize + SLOP) {
 			dstalloc = dstsize + SLOP;
 			dst = xrealloc(dst, dstalloc);
 		}
 	}
 	if (close(pipe_feed[0])) {
 		error("read from external filter %s failed", cmd);
 		free(dst);
 		dst = NULL;
 	}

 	status = finish_command(&child_process);
 	if (status) {
 		error("external filter %s failed %d", cmd, -status);
 		free(dst);
 		dst = NULL;
 	}

 	if (dst)
 		*sizep = dstsize;
 	return dst;
 }

 static struct convert_driver {
 	const char *name;
 	struct convert_driver *next;
 	char *smudge;
 	char *clean;
 } *user_convert, **user_convert_tail;

 static int read_convert_config(const char *var, const char *value)
 {
 	const char *ep, *name;
 	int namelen;
 	struct convert_driver *drv;

 	/*
 	 * External conversion drivers are configured using
 	 * "filter.<name>.variable".
 	 */
 	if (prefixcmp(var, "filter.") || (ep = strrchr(var, '.')) == var + 6)
 		return 0;
 	name = var + 7;
 	namelen = ep - name;
 	for (drv = user_convert; drv; drv = drv->next)
 		if (!strncmp(drv->name, name, namelen) && !drv->name[namelen])
 			break;
 	if (!drv) {
 		char *namebuf;
 		drv = xcalloc(1, sizeof(struct convert_driver));
 		namebuf = xmalloc(namelen + 1);
 		memcpy(namebuf, name, namelen);
 		namebuf[namelen] = 0;
 		drv->name = namebuf;
 		drv->next = NULL;
 		*user_convert_tail = drv;
 		user_convert_tail = &(drv->next);
 	}

 	ep++;

 	/*
 	 * filter.<name>.smudge and filter.<name>.clean specifies
 	 * the command line:
 	 *
 	 *	command-line
 	 *
 	 * The command-line will not be interpolated in any way.
 	 */

 	if (!strcmp("smudge", ep)) {
 		if (!value)
 			return error("%s: lacks value", var);
 		drv->smudge = strdup(value);
 		return 0;
 	}

 	if (!strcmp("clean", ep)) {
 		if (!value)
 			return error("%s: lacks value", var);
 		drv->clean = strdup(value);
 		return 0;
 	}
 	return 0;
 }

 static void setup_convert_check(struct git_attr_check *check)
 {
 	static struct git_attr *attr_crlf;
 	static struct git_attr *attr_ident;
 	static struct git_attr *attr_filter;

 	if (!attr_crlf) {
 		attr_crlf = git_attr("crlf", 4);
 		attr_ident = git_attr("ident", 5);
 		attr_filter = git_attr("filter", 6);
 		user_convert_tail = &user_convert;
 		git_config(read_convert_config);
 	}
 	check[0].attr = attr_crlf;
 	check[1].attr = attr_ident;
 	check[2].attr = attr_filter;
 }

 static int count_ident(const char *cp, unsigned long size)
 {
 	/*
 	 * "$Id: 0000000000000000000000000000000000000000 $" <=> "$Id$"
 	 */
 	int cnt = 0;
 	char ch;

 	while (size) {
 		ch = *cp++;
 		size--;
 		if (ch != '$')
 			continue;
 		if (size < 3)
 			break;
 		if (memcmp("Id", cp, 2))
 			continue;
 		ch = cp[2];
 		cp += 3;
 		size -= 3;
 		if (ch == '$')
 			cnt++; /* $Id$ */
 		if (ch != ':')
 			continue;

 		/*
 		 * "$Id: ... "; scan up to the closing dollar sign and discard.
 		 */
 		while (size) {
 			ch = *cp++;
 			size--;
 			if (ch == '$') {
 				cnt++;
 				break;
 			}
 		}
 	}
 	return cnt;
 }

 static char *ident_to_git(const char *path, const char *src, unsigned long *sizep, int ident)
 {
 	int cnt;
 	unsigned long size;
 	char *dst, *buf;

 	if (!ident)
 		return NULL;
 	size = *sizep;
 	cnt = count_ident(src, size);
 	if (!cnt)
 		return NULL;
 	buf = xmalloc(size);

 	for (dst = buf; size; size--) {
 		char ch = *src++;
 		*dst++ = ch;
 		if ((ch == '$') && (3 <= size) &&
 		    !memcmp("Id:", src, 3)) {
 			unsigned long rem = size - 3;
 			const char *cp = src + 3;
 			do {
 				ch = *cp++;
 				if (ch == '$')
 					break;
 				rem--;
 			} while (rem);
 			if (!rem)
 				continue;
 			memcpy(dst, "Id$", 3);
 			dst += 3;
 			size -= (cp - src);
 			src = cp;
 		}
 	}

 	*sizep = dst - buf;
 	return buf;
 }

 static char *ident_to_worktree(const char *path, const char *src, unsigned long *sizep, int ident)
 {
 	int cnt;
 	unsigned long size;
 	char *dst, *buf;
 	unsigned char sha1[20];

 	if (!ident)
 		return NULL;

 	size = *sizep;
 	cnt = count_ident(src, size);
 	if (!cnt)
 		return NULL;

 	hash_sha1_file(src, size, "blob", sha1);
 	buf = xmalloc(size + cnt * 43);

 	for (dst = buf; size; size--) {
 		const char *cp;
 		/* Fetch next source character, move the pointer on */
 		char ch = *src++;
 		/* Copy the current character to the destination */
 		*dst++ = ch;
 		/* If the current character is "$" or there are less than three
 		 * remaining bytes or the two bytes following this one are not
 		 * "Id", then simply read the next character */
 		if ((ch != '$') || (size < 3) || memcmp("Id", src, 2))
 			continue;
 		/*
 		 * Here when
 		 *  - There are more than 2 bytes remaining
 		 *  - The current three bytes are "$Id"
 		 * with
 		 *  - ch == "$"
 		 *  - src[0] == "I"
 		 */

 		/*
 		 * It's possible that an expanded Id has crept its way into the
 		 * repository, we cope with that by stripping the expansion out
 		 */
 		if (src[2] == ':') {
 			/* Expanded keywords have "$Id:" at the front */

 			/* discard up to but not including the closing $ */
 			unsigned long rem = size - 3;
 			/* Point at first byte after the ":" */
 			cp = src + 3;
 			/*
 			 * Throw away characters until either
 			 *  - we reach a "$"
 			 *  - we run out of bytes (rem == 0)
 			 */
 			do {
 				ch = *cp;
 				if (ch == '$')
 					break;
 				cp++;
 				rem--;
 			} while (rem);
 			/* If the above finished because it ran out of characters, then
 			 * this is an incomplete keyword, so don't run the expansion */
 			if (!rem)
 				continue;
 		} else if (src[2] == '$')
 			cp = src + 2;
 		else
 			/* Anything other than "$Id:XXX$" or $Id$ and we skip the
 			 * expansion */
 			continue;

 		/* cp is now pointing at the last $ of the keyword */

 		memcpy(dst, "Id: ", 4);
 		dst += 4;
 		memcpy(dst, sha1_to_hex(sha1), 40);
 		dst += 40;
 		*dst++ = ' ';

 		/* Adjust for the characters we've discarded */
 		size -= (cp - src);
 		src = cp;

 		/* Copy the final "$" */
 		*dst++ = *src++;
 		size--;
 	}

 	*sizep = dst - buf;
 	return buf;
 }

 static int git_path_check_crlf(const char *path, struct git_attr_check *check)
 {
 	const char *value = check->value;

 	if (ATTR_TRUE(value))
 		return CRLF_TEXT;
 	else if (ATTR_FALSE(value))
 		return CRLF_BINARY;
 	else if (ATTR_UNSET(value))
 		;
 	else if (!strcmp(value, "input"))
 		return CRLF_INPUT;
 	return CRLF_GUESS;
 }

 static struct convert_driver *git_path_check_convert(const char *path,
 					     struct git_attr_check *check)
 {
 	const char *value = check->value;
 	struct convert_driver *drv;

 	if (ATTR_TRUE(value) || ATTR_FALSE(value) || ATTR_UNSET(value))
 		return NULL;
 	for (drv = user_convert; drv; drv = drv->next)
 		if (!strcmp(value, drv->name))
 			return drv;
 	return NULL;
 }

 static int git_path_check_ident(const char *path, struct git_attr_check *check)
 {
 	const char *value = check->value;

 	return !!ATTR_TRUE(value);
 }

 char *convert_to_git(const char *path, const char *src, unsigned long *sizep)
 {
 	struct git_attr_check check[3];
 	int crlf = CRLF_GUESS;
 	int ident = 0;
 	char *filter = NULL;
 	char *buf, *buf2;

 	setup_convert_check(check);
 	if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
 		struct convert_driver *drv;
 		crlf = git_path_check_crlf(path, check + 0);
 		ident = git_path_check_ident(path, check + 1);
 		drv = git_path_check_convert(path, check + 2);
 		if (drv && drv->clean)
 			filter = drv->clean;
 	}

 	buf = apply_filter(path, src, sizep, filter);

 	buf2 = crlf_to_git(path, buf ? buf : src, sizep, crlf);
 	if (buf2) {
 		free(buf);
 		buf = buf2;
 	}

 	buf2 = ident_to_git(path, buf ? buf : src, sizep, ident);
 	if (buf2) {
 		free(buf);
 		buf = buf2;
 	}

 	return buf;
 }

 char *convert_to_working_tree(const char *path, const char *src, unsigned long *sizep)
 {
 	struct git_attr_check check[3];
 	int crlf = CRLF_GUESS;
 	int ident = 0;
 	char *filter = NULL;
 	char *buf, *buf2;

 	setup_convert_check(check);
 	if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
 		struct convert_driver *drv;
 		crlf = git_path_check_crlf(path, check + 0);
 		ident = git_path_check_ident(path, check + 1);
 		drv = git_path_check_convert(path, check + 2);
 		if (drv && drv->smudge)
 			filter = drv->smudge;
 	}

 	buf = ident_to_worktree(path, src, sizep, ident);

 	buf2 = crlf_to_worktree(path, buf ? buf : src, sizep, crlf);
 	if (buf2) {
 		free(buf);
 		buf = buf2;
 	}

 	buf2 = apply_filter(path, buf ? buf : src, sizep, filter);
 	if (buf2) {
 		free(buf);
 		buf = buf2;
 	}

 	return buf;
 }

 void *convert_sha1_file(const char *path, const unsigned char *sha1,
                         unsigned int mode, enum object_type *type,
                         unsigned long *size)
 {
 	void *buffer = read_sha1_file(sha1, type, size);
 	if (S_ISREG(mode) && buffer) {
 		void *converted = convert_to_working_tree(path, buffer, size);
 		if (converted) {
 			free(buffer);
 			buffer = converted;
 		}
 	}
 	return buffer;
 }
	#include "cache.h"
	#include "attr.h"
	#include "run-command.h"

	/*
	* convert.c - convert a file when checking it out and checking it in.
	*
	* This should use the pathname to decide on whether it wants to do some
	* more interesting conversions (automatic gzip/unzip, general format
	* conversions etc etc), but by default it just does automatic CRLF<->LF
	* translation when the "auto_crlf" option is set.
	*/

	#define CRLF_GUESS (-1)
	#define CRLF_BINARY 0
	#define CRLF_TEXT 1
	#define CRLF_INPUT 2

	struct text_stat {
	/* CR, LF and CRLF counts */
	unsigned cr, lf, crlf;

	/* These are just approximations! */
	unsigned printable, nonprintable;
	};

	static void gather_stats(const char buf, unsigned long size, struct text_stat stats)
	{
	unsigned long i;

	memset(stats, 0, sizeof(*stats));

	for (i = 0; i < size; i++) {
	unsigned char c = buf[i];
	if (c == '\r') {
	stats->cr++;
	if (i+1 < size && buf[i+1] == '\n')
	stats->crlf++;
	continue;
	}
	if (c == '\n') {
	stats->lf++;
	continue;
	}
	if (c == 127)
	/* DEL */
	stats->nonprintable++;
	else if (c < 32) {
	switch (c) {
	/* BS, HT, ESC and FF */
	case '\b': case '\t': case '\033': case '\014':
	stats->printable++;
	break;
	default:
	stats->nonprintable++;
	}
	}
	else
	stats->printable++;
	}
	}

	/*
	* The same heuristics as diff.c::mmfile_is_binary()
	*/
	static int is_binary(unsigned long size, struct text_stat *stats)
	{

	if ((stats->printable >> 7) < stats->nonprintable)
	return 1;
	/*
	* Other heuristics? Average line length might be relevant,
	* as might LF vs CR vs CRLF counts..
	*
	* NOTE! It might be normal to have a low ratio of CRLF to LF
	* (somebody starts with a LF-only file and edits it with an editor
	* that adds CRLF only to lines that are added..). But do we
	* want to support CR-only? Probably not.
	*/
	return 0;
	}

	static char crlf_to_git(const char path, const char src, unsigned long sizep, int action)
	{
	char buffer, dst;
	unsigned long size, nsize;
	struct text_stat stats;

	if ((action == CRLF_BINARY) \|\| !auto_crlf)
	return NULL;

	size = *sizep;
	if (!size)
	return NULL;

	gather_stats(src, size, &stats);

	/* No CR? Nothing to convert, regardless. */
	if (!stats.cr)
	return NULL;

	if (action == CRLF_GUESS) {
	/*
	* We're currently not going to even try to convert stuff
	* that has bare CR characters. Does anybody do that crazy
	* stuff?
	*/
	if (stats.cr != stats.crlf)
	return NULL;

	/*
	* And add some heuristics for binary vs text, of course...
	*/
	if (is_binary(size, &stats))
	return NULL;
	}

	/*
	* Ok, allocate a new buffer, fill it in, and return it
	* to let the caller know that we switched buffers.
	*/
	nsize = size - stats.crlf;
	buffer = xmalloc(nsize);
	*sizep = nsize;

	dst = buffer;
	if (action == CRLF_GUESS) {
	/*
	* If we guessed, we already know we rejected a file with
	* lone CR, and we can strip a CR without looking at what
	* follow it.
	*/
	do {
	unsigned char c = *src++;
	if (c != '\r')
	*dst++ = c;
	} while (--size);
	} else {
	do {
	unsigned char c = *src++;
	if (! (c == '\r' && (1 < size && *src == '\n')))
	*dst++ = c;
	} while (--size);
	}

	return buffer;
	}

	static char crlf_to_worktree(const char path, const char src, unsigned long sizep, int action)
	{
	char buffer, dst;
	unsigned long size, nsize;
	struct text_stat stats;
	unsigned char last;

	if ((action == CRLF_BINARY) \|\| (action == CRLF_INPUT) \|\|
	auto_crlf <= 0)
	return NULL;

	size = *sizep;
	if (!size)
	return NULL;

	gather_stats(src, size, &stats);

	/* No LF? Nothing to convert, regardless. */
	if (!stats.lf)
	return NULL;

	/* Was it already in CRLF format? */
	if (stats.lf == stats.crlf)
	return NULL;

	if (action == CRLF_GUESS) {
	/* If we have any bare CR characters, we're not going to touch it */
	if (stats.cr != stats.crlf)
	return NULL;

	if (is_binary(size, &stats))
	return NULL;
	}

	/*
	* Ok, allocate a new buffer, fill it in, and return it
	* to let the caller know that we switched buffers.
	*/
	nsize = size + stats.lf - stats.crlf;
	buffer = xmalloc(nsize);
	*sizep = nsize;
	last = 0;

	dst = buffer;
	do {
	unsigned char c = *src++;
	if (c == '\n' && last != '\r')
	*dst++ = '\r';
	*dst++ = c;
	last = c;
	} while (--size);

	return buffer;
	}

	static int filter_buffer(const char path, const char src,
	unsigned long size, const char *cmd)
	{
	/*
	* Spawn cmd and feed the buffer contents through its stdin.
	*/
	struct child_process child_process;
	int pipe_feed[2];
	int write_err, status;

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

	if (pipe(pipe_feed) < 0) {
	error("cannot create pipe to run external filter %s", cmd);
	return 1;
	}

	child_process.pid = fork();
	if (child_process.pid < 0) {
	error("cannot fork to run external filter %s", cmd);
	close(pipe_feed[0]);
	close(pipe_feed[1]);
	return 1;
	}
	if (!child_process.pid) {
	dup2(pipe_feed[0], 0);
	close(pipe_feed[0]);
	close(pipe_feed[1]);
	execlp("sh", "sh", "-c", cmd, NULL);
	return 1;
	}
	close(pipe_feed[0]);

	write_err = (write_in_full(pipe_feed[1], src, size) < 0);
	if (close(pipe_feed[1]))
	write_err = 1;
	if (write_err)
	error("cannot feed the input to external filter %s", cmd);

	status = finish_command(&child_process);
	if (status)
	error("external filter %s failed %d", cmd, -status);
	return (write_err \|\| status);
	}

	static char apply_filter(const char path, const char *src,
	unsigned long sizep, const char cmd)
	{
	/*
	* Create a pipeline to have the command filter the buffer's
	* contents.
	*
	* (child --> cmd) --> us
	*/
	const int SLOP = 4096;
	int pipe_feed[2];
	int status;
	char *dst;
	unsigned long dstsize, dstalloc;
	struct child_process child_process;

	if (!cmd)
	return NULL;

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

	if (pipe(pipe_feed) < 0) {
	error("cannot create pipe to run external filter %s", cmd);
	return NULL;
	}

	fflush(NULL);
	child_process.pid = fork();
	if (child_process.pid < 0) {
	error("cannot fork to run external filter %s", cmd);
	close(pipe_feed[0]);
	close(pipe_feed[1]);
	return NULL;
	}
	if (!child_process.pid) {
	dup2(pipe_feed[1], 1);
	close(pipe_feed[0]);
	close(pipe_feed[1]);
	exit(filter_buffer(path, src, *sizep, cmd));
	}
	close(pipe_feed[1]);

	dstalloc = *sizep;
	dst = xmalloc(dstalloc);
	dstsize = 0;

	while (1) {
	ssize_t numread = xread(pipe_feed[0], dst + dstsize,
	dstalloc - dstsize);

	if (numread <= 0) {
	if (!numread)
	break;
	error("read from external filter %s failed", cmd);
	free(dst);
	dst = NULL;
	break;
	}
	dstsize += numread;
	if (dstalloc <= dstsize + SLOP) {
	dstalloc = dstsize + SLOP;
	dst = xrealloc(dst, dstalloc);
	}
	}
	if (close(pipe_feed[0])) {
	error("read from external filter %s failed", cmd);
	free(dst);
	dst = NULL;
	}

	status = finish_command(&child_process);
	if (status) {
	error("external filter %s failed %d", cmd, -status);
	free(dst);
	dst = NULL;
	}

	if (dst)
	*sizep = dstsize;
	return dst;
	}

	static struct convert_driver {
	const char *name;
	struct convert_driver *next;
	char *smudge;
	char *clean;
	} user_convert, *user_convert_tail;

	static int read_convert_config(const char var, const char value)
	{
	const char ep, name;
	int namelen;
	struct convert_driver *drv;

	/*
	* External conversion drivers are configured using
	* "filter.<name>.variable".
	*/
	if (prefixcmp(var, "filter.") \|\| (ep = strrchr(var, '.')) == var + 6)
	return 0;
	name = var + 7;
	namelen = ep - name;
	for (drv = user_convert; drv; drv = drv->next)
	if (!strncmp(drv->name, name, namelen) && !drv->name[namelen])
	break;
	if (!drv) {
	char *namebuf;
	drv = xcalloc(1, sizeof(struct convert_driver));
	namebuf = xmalloc(namelen + 1);
	memcpy(namebuf, name, namelen);
	namebuf[namelen] = 0;
	drv->name = namebuf;
	drv->next = NULL;
	*user_convert_tail = drv;
	user_convert_tail = &(drv->next);
	}

	ep++;

	/*
	* filter.<name>.smudge and filter.<name>.clean specifies
	* the command line:
	*
	* command-line
	*
	* The command-line will not be interpolated in any way.
	*/

	if (!strcmp("smudge", ep)) {
	if (!value)
	return error("%s: lacks value", var);
	drv->smudge = strdup(value);
	return 0;
	}

	if (!strcmp("clean", ep)) {
	if (!value)
	return error("%s: lacks value", var);
	drv->clean = strdup(value);
	return 0;
	}
	return 0;
	}

	static void setup_convert_check(struct git_attr_check *check)
	{
	static struct git_attr *attr_crlf;
	static struct git_attr *attr_ident;
	static struct git_attr *attr_filter;

	if (!attr_crlf) {
	attr_crlf = git_attr("crlf", 4);
	attr_ident = git_attr("ident", 5);
	attr_filter = git_attr("filter", 6);
	user_convert_tail = &user_convert;
	git_config(read_convert_config);
	}
	check[0].attr = attr_crlf;
	check[1].attr = attr_ident;
	check[2].attr = attr_filter;
	}

	static int count_ident(const char *cp, unsigned long size)
	{
	/*
	* "$Id: 0000000000000000000000000000000000000000 $" <=> "$Id$"
	*/
	int cnt = 0;
	char ch;

	while (size) {
	ch = *cp++;
	size--;
	if (ch != '$')
	continue;
	if (size < 3)
	break;
	if (memcmp("Id", cp, 2))
	continue;
	ch = cp[2];
	cp += 3;
	size -= 3;
	if (ch == '$')
	cnt++; /* $Id$ */
	if (ch != ':')
	continue;

	/*
	* "$Id: ... "; scan up to the closing dollar sign and discard.
	*/
	while (size) {
	ch = *cp++;
	size--;
	if (ch == '$') {
	cnt++;
	break;
	}
	}
	}
	return cnt;
	}

	static char ident_to_git(const char path, const char src, unsigned long sizep, int ident)
	{
	int cnt;
	unsigned long size;
	char dst, buf;

	if (!ident)
	return NULL;
	size = *sizep;
	cnt = count_ident(src, size);
	if (!cnt)
	return NULL;
	buf = xmalloc(size);

	for (dst = buf; size; size--) {
	char ch = *src++;
	*dst++ = ch;
	if ((ch == '$') && (3 <= size) &&
	!memcmp("Id:", src, 3)) {
	unsigned long rem = size - 3;
	const char *cp = src + 3;
	do {
	ch = *cp++;
	if (ch == '$')
	break;
	rem--;
	} while (rem);
	if (!rem)
	continue;
	memcpy(dst, "Id$", 3);
	dst += 3;
	size -= (cp - src);
	src = cp;
	}
	}

	*sizep = dst - buf;
	return buf;
	}

	static char ident_to_worktree(const char path, const char src, unsigned long sizep, int ident)
	{
	int cnt;
	unsigned long size;
	char dst, buf;
	unsigned char sha1[20];

	if (!ident)
	return NULL;

	size = *sizep;
	cnt = count_ident(src, size);
	if (!cnt)
	return NULL;

	hash_sha1_file(src, size, "blob", sha1);
	buf = xmalloc(size + cnt * 43);

	for (dst = buf; size; size--) {
	const char *cp;
	/* Fetch next source character, move the pointer on */
	char ch = *src++;
	/* Copy the current character to the destination */
	*dst++ = ch;
	/* If the current character is "$" or there are less than three
	* remaining bytes or the two bytes following this one are not
	* "Id", then simply read the next character */
	if ((ch != '$') \|\| (size < 3) \|\| memcmp("Id", src, 2))
	continue;
	/*
	* Here when
	* - There are more than 2 bytes remaining
	* - The current three bytes are "$Id"
	* with
	* - ch == "$"
	* - src[0] == "I"
	*/

	/*
	* It's possible that an expanded Id has crept its way into the
	* repository, we cope with that by stripping the expansion out
	*/
	if (src[2] == ':') {
	/* Expanded keywords have "$Id:" at the front */

	/* discard up to but not including the closing $ */
	unsigned long rem = size - 3;
	/* Point at first byte after the ":" */
	cp = src + 3;
	/*
	* Throw away characters until either
	* - we reach a "$"
	* - we run out of bytes (rem == 0)
	*/
	do {
	ch = *cp;
	if (ch == '$')
	break;
	cp++;
	rem--;
	} while (rem);
	/* If the above finished because it ran out of characters, then
	* this is an incomplete keyword, so don't run the expansion */
	if (!rem)
	continue;
	} else if (src[2] == '$')
	cp = src + 2;
	else
	/* Anything other than "$Id:XXX$" or $Id$ and we skip the
	* expansion */
	continue;

	/* cp is now pointing at the last $ of the keyword */

	memcpy(dst, "Id: ", 4);
	dst += 4;
	memcpy(dst, sha1_to_hex(sha1), 40);
	dst += 40;
	*dst++ = ' ';

	/* Adjust for the characters we've discarded */
	size -= (cp - src);
	src = cp;

	/* Copy the final "$" */
	dst++ = src++;
	size--;
	}

	*sizep = dst - buf;
	return buf;
	}

	static int git_path_check_crlf(const char path, struct git_attr_check check)
	{
	const char *value = check->value;

	if (ATTR_TRUE(value))
	return CRLF_TEXT;
	else if (ATTR_FALSE(value))
	return CRLF_BINARY;
	else if (ATTR_UNSET(value))
	;
	else if (!strcmp(value, "input"))
	return CRLF_INPUT;
	return CRLF_GUESS;
	}

	static struct convert_driver git_path_check_convert(const char path,
	struct git_attr_check *check)
	{
	const char *value = check->value;
	struct convert_driver *drv;

	if (ATTR_TRUE(value) \|\| ATTR_FALSE(value) \|\| ATTR_UNSET(value))
	return NULL;
	for (drv = user_convert; drv; drv = drv->next)
	if (!strcmp(value, drv->name))
	return drv;
	return NULL;
	}

	static int git_path_check_ident(const char path, struct git_attr_check check)
	{
	const char *value = check->value;

	return !!ATTR_TRUE(value);
	}

	char convert_to_git(const char path, const char src, unsigned long sizep)
	{
	struct git_attr_check check[3];
	int crlf = CRLF_GUESS;
	int ident = 0;
	char *filter = NULL;
	char buf, buf2;

	setup_convert_check(check);
	if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
	struct convert_driver *drv;
	crlf = git_path_check_crlf(path, check + 0);
	ident = git_path_check_ident(path, check + 1);
	drv = git_path_check_convert(path, check + 2);
	if (drv && drv->clean)
	filter = drv->clean;
	}

	buf = apply_filter(path, src, sizep, filter);

	buf2 = crlf_to_git(path, buf ? buf : src, sizep, crlf);
	if (buf2) {
	free(buf);
	buf = buf2;
	}

	buf2 = ident_to_git(path, buf ? buf : src, sizep, ident);
	if (buf2) {
	free(buf);
	buf = buf2;
	}

	return buf;
	}

	char convert_to_working_tree(const char path, const char src, unsigned long sizep)
	{
	struct git_attr_check check[3];
	int crlf = CRLF_GUESS;
	int ident = 0;
	char *filter = NULL;
	char buf, buf2;

	setup_convert_check(check);
	if (!git_checkattr(path, ARRAY_SIZE(check), check)) {
	struct convert_driver *drv;
	crlf = git_path_check_crlf(path, check + 0);
	ident = git_path_check_ident(path, check + 1);
	drv = git_path_check_convert(path, check + 2);
	if (drv && drv->smudge)
	filter = drv->smudge;
	}

	buf = ident_to_worktree(path, src, sizep, ident);

	buf2 = crlf_to_worktree(path, buf ? buf : src, sizep, crlf);
	if (buf2) {
	free(buf);
	buf = buf2;
	}

	buf2 = apply_filter(path, buf ? buf : src, sizep, filter);
	if (buf2) {
	free(buf);
	buf = buf2;
	}

	return buf;
	}

	void convert_sha1_file(const char path, const unsigned char *sha1,
	unsigned int mode, enum object_type *type,
	unsigned long *size)
	{
	void *buffer = read_sha1_file(sha1, type, size);
	if (S_ISREG(mode) && buffer) {
	void *converted = convert_to_working_tree(path, buffer, size);
	if (converted) {
	free(buffer);
	buffer = converted;
	}
	}
	return buffer;
	}