config.c - jrn/git - Git at Google

 /*
  * GIT - The information manager from hell
  *
  * Copyright (C) Linus Torvalds, 2005
  * Copyright (C) Johannes Schindelin, 2005
  *
  */
 #include "cache.h"
 #include <regex.h>

 #define MAXNAME (256)

 static FILE *config_file;
 static const char *config_file_name;
 static int config_linenr;
 static int get_next_char(void)
 {
 	int c;
 	FILE *f;

 	c = '\n';
 	if ((f = config_file) != NULL) {
 		c = fgetc(f);
 		if (c == '\r') {
 			/* DOS like systems */
 			c = fgetc(f);
 			if (c != '\n') {
 				ungetc(c, f);
 				c = '\r';
 			}
 		}
 		if (c == '\n')
 			config_linenr++;
 		if (c == EOF) {
 			config_file = NULL;
 			c = '\n';
 		}
 	}
 	return c;
 }

 static char *parse_value(void)
 {
 	static char value[1024];
 	int quote = 0, comment = 0, len = 0, space = 0;

 	for (;;) {
 		int c = get_next_char();
 		if (len >= sizeof(value))
 			return NULL;
 		if (c == '\n') {
 			if (quote)
 				return NULL;
 			value[len] = 0;
 			return value;
 		}
 		if (comment)
 			continue;
 		if (isspace(c) && !quote) {
 			space = 1;
 			continue;
 		}
 		if (space) {
 			if (len)
 				value[len++] = ' ';
 			space = 0;
 		}
 		if (c == '\\') {
 			c = get_next_char();
 			switch (c) {
 			case '\n':
 				continue;
 			case 't':
 				c = '\t';
 				break;
 			case 'b':
 				c = '\b';
 				break;
 			case 'n':
 				c = '\n';
 				break;
 			/* Some characters escape as themselves */
 			case '\\': case '"':
 				break;
 			/* Reject unknown escape sequences */
 			default:
 				return NULL;
 			}
 			value[len++] = c;
 			continue;
 		}
 		if (c == '"') {
 			quote = 1-quote;
 			continue;
 		}
 		if (!quote) {
 			if (c == ';' || c == '#') {
 				comment = 1;
 				continue;
 			}
 		}
 		value[len++] = c;
 	}
 }

 static int get_value(config_fn_t fn, char *name, unsigned int len)
 {
 	int c;
 	char *value;

 	/* Get the full name */
 	for (;;) {
 		c = get_next_char();
 		if (c == EOF)
 			break;
 		if (!isalnum(c))
 			break;
 		name[len++] = tolower(c);
 		if (len >= MAXNAME)
 			return -1;
 	}
 	name[len] = 0;
 	while (c == ' ' || c == '\t')
 		c = get_next_char();

 	value = NULL;
 	if (c != '\n') {
 		if (c != '=')
 			return -1;
 		value = parse_value();
 		if (!value)
 			return -1;
 	}
 	return fn(name, value);
 }

 static int get_base_var(char *name)
 {
 	int baselen = 0;

 	for (;;) {
 		int c = get_next_char();
 		if (c == EOF)
 			return -1;
 		if (c == ']')
 			return baselen;
 		if (!isalnum(c) && c != '.')
 			return -1;
 		if (baselen > MAXNAME / 2)
 			return -1;
 		name[baselen++] = tolower(c);
 	}
 }

 static int git_parse_file(config_fn_t fn)
 {
 	int comment = 0;
 	int baselen = 0;
 	static char var[MAXNAME];

 	for (;;) {
 		int c = get_next_char();
 		if (c == '\n') {
 			/* EOF? */
 			if (!config_file)
 				return 0;
 			comment = 0;
 			continue;
 		}
 		if (comment || isspace(c))
 			continue;
 		if (c == '#' || c == ';') {
 			comment = 1;
 			continue;
 		}
 		if (c == '[') {
 			baselen = get_base_var(var);
 			if (baselen <= 0)
 				break;
 			var[baselen++] = '.';
 			var[baselen] = 0;
 			continue;
 		}
 		if (!isalpha(c))
 			break;
 		var[baselen] = tolower(c);
 		if (get_value(fn, var, baselen+1) < 0)
 			break;
 	}
 	die("bad config file line %d in %s", config_linenr, config_file_name);
 }

 int git_config_int(const char *name, const char *value)
 {
 	if (value && *value) {
 		char *end;
 		int val = strtol(value, &end, 0);
 		if (!*end)
 			return val;
 	}
 	die("bad config value for '%s' in %s", name, config_file_name);
 }

 int git_config_bool(const char *name, const char *value)
 {
 	if (!value)
 		return 1;
 	if (!*value)
 		return 0;
 	if (!strcasecmp(value, "true"))
 		return 1;
 	if (!strcasecmp(value, "false"))
 		return 0;
 	return git_config_int(name, value) != 0;
 }

 int git_default_config(const char *var, const char *value)
 {
 	/* This needs a better name */
 	if (!strcmp(var, "core.filemode")) {
 		trust_executable_bit = git_config_bool(var, value);
 		return 0;
 	}

 	if (!strcmp(var, "core.ignorestat")) {
 		assume_unchanged = git_config_bool(var, value);
 		return 0;
 	}

 	if (!strcmp(var, "core.symrefsonly")) {
 		only_use_symrefs = git_config_bool(var, value);
 		return 0;
 	}

 	if (!strcmp(var, "core.warnambiguousrefs")) {
 		warn_ambiguous_refs = git_config_bool(var, value);
 		return 0;
 	}

 	if (!strcmp(var, "user.name")) {
 		strncpy(git_default_name, value, sizeof(git_default_name));
 		return 0;
 	}

 	if (!strcmp(var, "user.email")) {
 		strncpy(git_default_email, value, sizeof(git_default_email));
 		return 0;
 	}

 	if (!strcmp(var, "i18n.commitencoding")) {
 		strncpy(git_commit_encoding, value, sizeof(git_commit_encoding));
 		return 0;
 	}

 	/* Add other config variables here.. */
 	return 0;
 }

 int git_config_from_file(config_fn_t fn, const char *filename)
 {
 	int ret;
 	FILE *f = fopen(filename, "r");

 	ret = -1;
 	if (f) {
 		config_file = f;
 		config_file_name = filename;
 		config_linenr = 1;
 		ret = git_parse_file(fn);
 		fclose(f);
 		config_file_name = NULL;
 	}
 	return ret;
 }

 int git_config(config_fn_t fn)
 {
 	return git_config_from_file(fn, git_path("config"));
 }

 /*
  * Find all the stuff for git_config_set() below.
  */

 #define MAX_MATCHES 512

 static struct {
 	int baselen;
 	char* key;
 	int do_not_match;
 	regex_t* value_regex;
 	int multi_replace;
 	off_t offset[MAX_MATCHES];
 	enum { START, SECTION_SEEN, SECTION_END_SEEN, KEY_SEEN } state;
 	int seen;
 } store;

 static int matches(const char* key, const char* value)
 {
 	return !strcmp(key, store.key) &&
 		(store.value_regex == NULL ||
 		 (store.do_not_match ^
 		  !regexec(store.value_regex, value, 0, NULL, 0)));
 }

 static int store_aux(const char* key, const char* value)
 {
 	switch (store.state) {
 	case KEY_SEEN:
 		if (matches(key, value)) {
 			if (store.seen == 1 && store.multi_replace == 0) {
 				fprintf(stderr,
 					"Warning: %s has multiple values\n",
 					key);
 			} else if (store.seen >= MAX_MATCHES) {
 				fprintf(stderr, "Too many matches\n");
 				return 1;
 			}

 			store.offset[store.seen] = ftell(config_file);
 			store.seen++;
 		}
 		break;
 	case SECTION_SEEN:
 		if (strncmp(key, store.key, store.baselen+1)) {
 			store.state = SECTION_END_SEEN;
 			break;
 		} else
 			/* do not increment matches: this is no match */
 			store.offset[store.seen] = ftell(config_file);
 		/* fallthru */
 	case SECTION_END_SEEN:
 	case START:
 		if (matches(key, value)) {
 			store.offset[store.seen] = ftell(config_file);
 			store.state = KEY_SEEN;
 			store.seen++;
 		} else if(!strncmp(key, store.key, store.baselen))
 			store.state = SECTION_SEEN;
 	}
 	return 0;
 }

 static void store_write_section(int fd, const char* key)
 {
 	write(fd, "[", 1);
 	write(fd, key, store.baselen);
 	write(fd, "]\n", 2);
 }

 static void store_write_pair(int fd, const char* key, const char* value)
 {
 	int i;

 	write(fd, "\t", 1);
 	write(fd, key+store.baselen+1,
 		strlen(key+store.baselen+1));
 	write(fd, " = ", 3);
 	for (i = 0; value[i]; i++)
 		switch (value[i]) {
 		case '\n': write(fd, "\\n", 2); break;
 		case '\t': write(fd, "\\t", 2); break;
 		case '"': case '\\': write(fd, "\\", 1);
 		default: write(fd, value+i, 1);
 	}
 	write(fd, "\n", 1);
 }

 static int find_beginning_of_line(const char* contents, int size,
 	int offset_, int* found_bracket)
 {
 	int equal_offset = size, bracket_offset = size;
 	int offset;

 	for (offset = offset_-2; offset > 0
 			&& contents[offset] != '\n'; offset--)
 		switch (contents[offset]) {
 			case '=': equal_offset = offset; break;
 			case ']': bracket_offset = offset; break;
 		}
 	if (bracket_offset < equal_offset) {
 		*found_bracket = 1;
 		offset = bracket_offset+1;
 	} else
 		offset++;

 	return offset;
 }

 int git_config_set(const char* key, const char* value)
 {
 	return git_config_set_multivar(key, value, NULL, 0);
 }

 /*
  * If value==NULL, unset in (remove from) config,
  * if value_regex!=NULL, disregard key/value pairs where value does not match.
  * if multi_replace==0, nothing, or only one matching key/value is replaced,
  *     else all matching key/values (regardless how many) are removed,
  *     before the new pair is written.
  *
  * Returns 0 on success.
  *
  * This function does this:
  *
  * - it locks the config file by creating ".git/config.lock"
  *
  * - it then parses the config using store_aux() as validator to find
  *   the position on the key/value pair to replace. If it is to be unset,
  *   it must be found exactly once.
  *
  * - the config file is mmap()ed and the part before the match (if any) is
  *   written to the lock file, then the changed part and the rest.
  *
  * - the config file is removed and the lock file rename()d to it.
  *
  */
 int git_config_set_multivar(const char* key, const char* value,
 	const char* value_regex, int multi_replace)
 {
 	int i;
 	int fd, in_fd;
 	char* config_filename = strdup(git_path("config"));
 	char* lock_file = strdup(git_path("config.lock"));
 	const char* last_dot = strrchr(key, '.');

 	/*
 	 * Since "key" actually contains the section name and the real
 	 * key name separated by a dot, we have to know where the dot is.
 	 */

 	if (last_dot == NULL) {
 		fprintf(stderr, "key does not contain a section: %s\n", key);
 		return 2;
 	}
 	store.baselen = last_dot - key;

 	store.multi_replace = multi_replace;

 	/*
 	 * Validate the key and while at it, lower case it for matching.
 	 */
 	store.key = (char*)malloc(strlen(key)+1);
 	for (i = 0; key[i]; i++)
 		if (i != store.baselen &&
 				((!isalnum(key[i]) && key[i] != '.') ||
 				 (i == store.baselen+1 && !isalpha(key[i])))) {
 			fprintf(stderr, "invalid key: %s\n", key);
 			free(store.key);
 			return 1;
 		} else
 			store.key[i] = tolower(key[i]);
 	store.key[i] = 0;

 	/*
 	 * The lock_file serves a purpose in addition to locking: the new
 	 * contents of .git/config will be written into it.
 	 */
 	fd = open(lock_file, O_WRONLY | O_CREAT | O_EXCL, 0666);
 	if (fd < 0) {
 		fprintf(stderr, "could not lock config file\n");
 		free(store.key);
 		return -1;
 	}

 	/*
 	 * If .git/config does not exist yet, write a minimal version.
 	 */
 	in_fd = open(config_filename, O_RDONLY);
 	if ( in_fd < 0 ) {
 		free(store.key);

 		if ( ENOENT != errno ) {
 			error("opening %s: %s", config_filename,
 			      strerror(errno));
 			close(fd);
 			unlink(lock_file);
 			return 3; /* same as "invalid config file" */
 		}
 		/* if nothing to unset, error out */
 		if (value == NULL) {
 			close(fd);
 			unlink(lock_file);
 			return 5;
 		}

 		store.key = (char*)key;
 		store_write_section(fd, key);
 		store_write_pair(fd, key, value);
 	} else{
 		struct stat st;
 		char* contents;
 		int i, copy_begin, copy_end, new_line = 0;

 		if (value_regex == NULL)
 			store.value_regex = NULL;
 		else {
 			if (value_regex[0] == '!') {
 				store.do_not_match = 1;
 				value_regex++;
 			} else
 				store.do_not_match = 0;

 			store.value_regex = (regex_t*)malloc(sizeof(regex_t));
 			if (regcomp(store.value_regex, value_regex,
 					REG_EXTENDED)) {
 				fprintf(stderr, "Invalid pattern: %s\n",
 					value_regex);
 				free(store.value_regex);
 				return 6;
 			}
 		}

 		store.offset[0] = 0;
 		store.state = START;
 		store.seen = 0;

 		/*
 		 * After this, store.offset will contain the *end* offset
 		 * of the last match, or remain at 0 if no match was found.
 		 * As a side effect, we make sure to transform only a valid
 		 * existing config file.
 		 */
 		if (git_config(store_aux)) {
 			fprintf(stderr, "invalid config file\n");
 			free(store.key);
 			if (store.value_regex != NULL) {
 				regfree(store.value_regex);
 				free(store.value_regex);
 			}
 			return 3;
 		}

 		free(store.key);
 		if (store.value_regex != NULL) {
 			regfree(store.value_regex);
 			free(store.value_regex);
 		}

 		/* if nothing to unset, or too many matches, error out */
 		if ((store.seen == 0 && value == NULL) ||
 				(store.seen > 1 && multi_replace == 0)) {
 			close(fd);
 			unlink(lock_file);
 			return 5;
 		}

 		fstat(in_fd, &st);
 		contents = mmap(NULL, st.st_size, PROT_READ,
 			MAP_PRIVATE, in_fd, 0);
 		close(in_fd);

 		if (store.seen == 0)
 			store.seen = 1;

 		for (i = 0, copy_begin = 0; i < store.seen; i++) {
 			if (store.offset[i] == 0) {
 				store.offset[i] = copy_end = st.st_size;
 			} else if (store.state != KEY_SEEN) {
 				copy_end = store.offset[i];
 			} else
 				copy_end = find_beginning_of_line(
 					contents, st.st_size,
 					store.offset[i]-2, &new_line);

 			/* write the first part of the config */
 			if (copy_end > copy_begin) {
 				write(fd, contents + copy_begin,
 				copy_end - copy_begin);
 				if (new_line)
 					write(fd, "\n", 1);
 			}
 			copy_begin = store.offset[i];
 		}

 		/* write the pair (value == NULL means unset) */
 		if (value != NULL) {
 			if (store.state == START)
 				store_write_section(fd, key);
 			store_write_pair(fd, key, value);
 		}

 		/* write the rest of the config */
 		if (copy_begin < st.st_size)
 			write(fd, contents + copy_begin,
 				st.st_size - copy_begin);

 		munmap(contents, st.st_size);
 		unlink(config_filename);
 	}

 	close(fd);

 	if (rename(lock_file, config_filename) < 0) {
 		fprintf(stderr, "Could not rename the lock file?\n");
 		return 4;
 	}

 	return 0;
 }
	/*
	* GIT - The information manager from hell
	*
	* Copyright (C) Linus Torvalds, 2005
	* Copyright (C) Johannes Schindelin, 2005
	*
	*/
	#include "cache.h"
	#include <regex.h>

	#define MAXNAME (256)

	static FILE *config_file;
	static const char *config_file_name;
	static int config_linenr;
	static int get_next_char(void)
	{
	int c;
	FILE *f;

	c = '\n';
	if ((f = config_file) != NULL) {
	c = fgetc(f);
	if (c == '\r') {
	/* DOS like systems */
	c = fgetc(f);
	if (c != '\n') {
	ungetc(c, f);
	c = '\r';
	}
	}
	if (c == '\n')
	config_linenr++;
	if (c == EOF) {
	config_file = NULL;
	c = '\n';
	}
	}
	return c;
	}

	static char *parse_value(void)
	{
	static char value[1024];
	int quote = 0, comment = 0, len = 0, space = 0;

	for (;;) {
	int c = get_next_char();
	if (len >= sizeof(value))
	return NULL;
	if (c == '\n') {
	if (quote)
	return NULL;
	value[len] = 0;
	return value;
	}
	if (comment)
	continue;
	if (isspace(c) && !quote) {
	space = 1;
	continue;
	}
	if (space) {
	if (len)
	value[len++] = ' ';
	space = 0;
	}
	if (c == '\\') {
	c = get_next_char();
	switch (c) {
	case '\n':
	continue;
	case 't':
	c = '\t';
	break;
	case 'b':
	c = '\b';
	break;
	case 'n':
	c = '\n';
	break;
	/* Some characters escape as themselves */
	case '\\': case '"':
	break;
	/* Reject unknown escape sequences */
	default:
	return NULL;
	}
	value[len++] = c;
	continue;
	}
	if (c == '"') {
	quote = 1-quote;
	continue;
	}
	if (!quote) {
	if (c == ';' \|\| c == '#') {
	comment = 1;
	continue;
	}
	}
	value[len++] = c;
	}
	}

	static int get_value(config_fn_t fn, char *name, unsigned int len)
	{
	int c;
	char *value;

	/* Get the full name */
	for (;;) {
	c = get_next_char();
	if (c == EOF)
	break;
	if (!isalnum(c))
	break;
	name[len++] = tolower(c);
	if (len >= MAXNAME)
	return -1;
	}
	name[len] = 0;
	while (c == ' ' \|\| c == '\t')
	c = get_next_char();

	value = NULL;
	if (c != '\n') {
	if (c != '=')
	return -1;
	value = parse_value();
	if (!value)
	return -1;
	}
	return fn(name, value);
	}

	static int get_base_var(char *name)
	{
	int baselen = 0;

	for (;;) {
	int c = get_next_char();
	if (c == EOF)
	return -1;
	if (c == ']')
	return baselen;
	if (!isalnum(c) && c != '.')
	return -1;
	if (baselen > MAXNAME / 2)
	return -1;
	name[baselen++] = tolower(c);
	}
	}

	static int git_parse_file(config_fn_t fn)
	{
	int comment = 0;
	int baselen = 0;
	static char var[MAXNAME];

	for (;;) {
	int c = get_next_char();
	if (c == '\n') {
	/* EOF? */
	if (!config_file)
	return 0;
	comment = 0;
	continue;
	}
	if (comment \|\| isspace(c))
	continue;
	if (c == '#' \|\| c == ';') {
	comment = 1;
	continue;
	}
	if (c == '[') {
	baselen = get_base_var(var);
	if (baselen <= 0)
	break;
	var[baselen++] = '.';
	var[baselen] = 0;
	continue;
	}
	if (!isalpha(c))
	break;
	var[baselen] = tolower(c);
	if (get_value(fn, var, baselen+1) < 0)
	break;
	}
	die("bad config file line %d in %s", config_linenr, config_file_name);
	}

	int git_config_int(const char name, const char value)
	{
	if (value && *value) {
	char *end;
	int val = strtol(value, &end, 0);
	if (!*end)
	return val;
	}
	die("bad config value for '%s' in %s", name, config_file_name);
	}

	int git_config_bool(const char name, const char value)
	{
	if (!value)
	return 1;
	if (!*value)
	return 0;
	if (!strcasecmp(value, "true"))
	return 1;
	if (!strcasecmp(value, "false"))
	return 0;
	return git_config_int(name, value) != 0;
	}

	int git_default_config(const char var, const char value)
	{
	/* This needs a better name */
	if (!strcmp(var, "core.filemode")) {
	trust_executable_bit = git_config_bool(var, value);
	return 0;
	}

	if (!strcmp(var, "core.ignorestat")) {
	assume_unchanged = git_config_bool(var, value);
	return 0;
	}

	if (!strcmp(var, "core.symrefsonly")) {
	only_use_symrefs = git_config_bool(var, value);
	return 0;
	}

	if (!strcmp(var, "core.warnambiguousrefs")) {
	warn_ambiguous_refs = git_config_bool(var, value);
	return 0;
	}

	if (!strcmp(var, "user.name")) {
	strncpy(git_default_name, value, sizeof(git_default_name));
	return 0;
	}

	if (!strcmp(var, "user.email")) {
	strncpy(git_default_email, value, sizeof(git_default_email));
	return 0;
	}

	if (!strcmp(var, "i18n.commitencoding")) {
	strncpy(git_commit_encoding, value, sizeof(git_commit_encoding));
	return 0;
	}

	/* Add other config variables here.. */
	return 0;
	}

	int git_config_from_file(config_fn_t fn, const char *filename)
	{
	int ret;
	FILE *f = fopen(filename, "r");

	ret = -1;
	if (f) {
	config_file = f;
	config_file_name = filename;
	config_linenr = 1;
	ret = git_parse_file(fn);
	fclose(f);
	config_file_name = NULL;
	}
	return ret;
	}

	int git_config(config_fn_t fn)
	{
	return git_config_from_file(fn, git_path("config"));
	}

	/*
	* Find all the stuff for git_config_set() below.
	*/

	#define MAX_MATCHES 512

	static struct {
	int baselen;
	char* key;
	int do_not_match;
	regex_t* value_regex;
	int multi_replace;
	off_t offset[MAX_MATCHES];
	enum { START, SECTION_SEEN, SECTION_END_SEEN, KEY_SEEN } state;
	int seen;
	} store;

	static int matches(const char* key, const char* value)
	{
	return !strcmp(key, store.key) &&
	(store.value_regex == NULL \|\|
	(store.do_not_match ^
	!regexec(store.value_regex, value, 0, NULL, 0)));
	}

	static int store_aux(const char* key, const char* value)
	{
	switch (store.state) {
	case KEY_SEEN:
	if (matches(key, value)) {
	if (store.seen == 1 && store.multi_replace == 0) {
	fprintf(stderr,
	"Warning: %s has multiple values\n",
	key);
	} else if (store.seen >= MAX_MATCHES) {
	fprintf(stderr, "Too many matches\n");
	return 1;
	}

	store.offset[store.seen] = ftell(config_file);
	store.seen++;
	}
	break;
	case SECTION_SEEN:
	if (strncmp(key, store.key, store.baselen+1)) {
	store.state = SECTION_END_SEEN;
	break;
	} else
	/* do not increment matches: this is no match */
	store.offset[store.seen] = ftell(config_file);
	/* fallthru */
	case SECTION_END_SEEN:
	case START:
	if (matches(key, value)) {
	store.offset[store.seen] = ftell(config_file);
	store.state = KEY_SEEN;
	store.seen++;
	} else if(!strncmp(key, store.key, store.baselen))
	store.state = SECTION_SEEN;
	}
	return 0;
	}

	static void store_write_section(int fd, const char* key)
	{
	write(fd, "[", 1);
	write(fd, key, store.baselen);
	write(fd, "]\n", 2);
	}

	static void store_write_pair(int fd, const char* key, const char* value)
	{
	int i;

	write(fd, "\t", 1);
	write(fd, key+store.baselen+1,
	strlen(key+store.baselen+1));
	write(fd, " = ", 3);
	for (i = 0; value[i]; i++)
	switch (value[i]) {
	case '\n': write(fd, "\\n", 2); break;
	case '\t': write(fd, "\\t", 2); break;
	case '"': case '\\': write(fd, "\\", 1);
	default: write(fd, value+i, 1);
	}
	write(fd, "\n", 1);
	}

	static int find_beginning_of_line(const char* contents, int size,
	int offset_, int* found_bracket)
	{
	int equal_offset = size, bracket_offset = size;
	int offset;

	for (offset = offset_-2; offset > 0
	&& contents[offset] != '\n'; offset--)
	switch (contents[offset]) {
	case '=': equal_offset = offset; break;
	case ']': bracket_offset = offset; break;
	}
	if (bracket_offset < equal_offset) {
	*found_bracket = 1;
	offset = bracket_offset+1;
	} else
	offset++;

	return offset;
	}

	int git_config_set(const char* key, const char* value)
	{
	return git_config_set_multivar(key, value, NULL, 0);
	}

	/*
	* If value==NULL, unset in (remove from) config,
	* if value_regex!=NULL, disregard key/value pairs where value does not match.
	* if multi_replace==0, nothing, or only one matching key/value is replaced,
	* else all matching key/values (regardless how many) are removed,
	* before the new pair is written.
	*
	* Returns 0 on success.
	*
	* This function does this:
	*
	* - it locks the config file by creating ".git/config.lock"
	*
	* - it then parses the config using store_aux() as validator to find
	* the position on the key/value pair to replace. If it is to be unset,
	* it must be found exactly once.
	*
	* - the config file is mmap()ed and the part before the match (if any) is
	* written to the lock file, then the changed part and the rest.
	*
	* - the config file is removed and the lock file rename()d to it.
	*
	*/
	int git_config_set_multivar(const char* key, const char* value,
	const char* value_regex, int multi_replace)
	{
	int i;
	int fd, in_fd;
	char* config_filename = strdup(git_path("config"));
	char* lock_file = strdup(git_path("config.lock"));
	const char* last_dot = strrchr(key, '.');

	/*
	* Since "key" actually contains the section name and the real
	* key name separated by a dot, we have to know where the dot is.
	*/

	if (last_dot == NULL) {
	fprintf(stderr, "key does not contain a section: %s\n", key);
	return 2;
	}
	store.baselen = last_dot - key;

	store.multi_replace = multi_replace;

	/*
	* Validate the key and while at it, lower case it for matching.
	*/
	store.key = (char*)malloc(strlen(key)+1);
	for (i = 0; key[i]; i++)
	if (i != store.baselen &&
	((!isalnum(key[i]) && key[i] != '.') \|\|
	(i == store.baselen+1 && !isalpha(key[i])))) {
	fprintf(stderr, "invalid key: %s\n", key);
	free(store.key);
	return 1;
	} else
	store.key[i] = tolower(key[i]);
	store.key[i] = 0;

	/*
	* The lock_file serves a purpose in addition to locking: the new
	* contents of .git/config will be written into it.
	*/
	fd = open(lock_file, O_WRONLY \| O_CREAT \| O_EXCL, 0666);
	if (fd < 0) {
	fprintf(stderr, "could not lock config file\n");
	free(store.key);
	return -1;
	}

	/*
	* If .git/config does not exist yet, write a minimal version.
	*/
	in_fd = open(config_filename, O_RDONLY);
	if ( in_fd < 0 ) {
	free(store.key);

	if ( ENOENT != errno ) {
	error("opening %s: %s", config_filename,
	strerror(errno));
	close(fd);
	unlink(lock_file);
	return 3; /* same as "invalid config file" */
	}
	/* if nothing to unset, error out */
	if (value == NULL) {
	close(fd);
	unlink(lock_file);
	return 5;
	}

	store.key = (char*)key;
	store_write_section(fd, key);
	store_write_pair(fd, key, value);
	} else{
	struct stat st;
	char* contents;
	int i, copy_begin, copy_end, new_line = 0;

	if (value_regex == NULL)
	store.value_regex = NULL;
	else {
	if (value_regex[0] == '!') {
	store.do_not_match = 1;
	value_regex++;
	} else
	store.do_not_match = 0;

	store.value_regex = (regex_t*)malloc(sizeof(regex_t));
	if (regcomp(store.value_regex, value_regex,
	REG_EXTENDED)) {
	fprintf(stderr, "Invalid pattern: %s\n",
	value_regex);
	free(store.value_regex);
	return 6;
	}
	}

	store.offset[0] = 0;
	store.state = START;
	store.seen = 0;

	/*
	* After this, store.offset will contain the end offset
	* of the last match, or remain at 0 if no match was found.
	* As a side effect, we make sure to transform only a valid
	* existing config file.
	*/
	if (git_config(store_aux)) {
	fprintf(stderr, "invalid config file\n");
	free(store.key);
	if (store.value_regex != NULL) {
	regfree(store.value_regex);
	free(store.value_regex);
	}
	return 3;
	}

	free(store.key);
	if (store.value_regex != NULL) {
	regfree(store.value_regex);
	free(store.value_regex);
	}

	/* if nothing to unset, or too many matches, error out */
	if ((store.seen == 0 && value == NULL) \|\|
	(store.seen > 1 && multi_replace == 0)) {
	close(fd);
	unlink(lock_file);
	return 5;
	}

	fstat(in_fd, &st);
	contents = mmap(NULL, st.st_size, PROT_READ,
	MAP_PRIVATE, in_fd, 0);
	close(in_fd);

	if (store.seen == 0)
	store.seen = 1;

	for (i = 0, copy_begin = 0; i < store.seen; i++) {
	if (store.offset[i] == 0) {
	store.offset[i] = copy_end = st.st_size;
	} else if (store.state != KEY_SEEN) {
	copy_end = store.offset[i];
	} else
	copy_end = find_beginning_of_line(
	contents, st.st_size,
	store.offset[i]-2, &new_line);

	/* write the first part of the config */
	if (copy_end > copy_begin) {
	write(fd, contents + copy_begin,
	copy_end - copy_begin);
	if (new_line)
	write(fd, "\n", 1);
	}
	copy_begin = store.offset[i];
	}

	/* write the pair (value == NULL means unset) */
	if (value != NULL) {
	if (store.state == START)
	store_write_section(fd, key);
	store_write_pair(fd, key, value);
	}

	/* write the rest of the config */
	if (copy_begin < st.st_size)
	write(fd, contents + copy_begin,
	st.st_size - copy_begin);

	munmap(contents, st.st_size);
	unlink(config_filename);
	}

	close(fd);

	if (rename(lock_file, config_filename) < 0) {
	fprintf(stderr, "Could not rename the lock file?\n");
	return 4;
	}

	return 0;
	}