builtin-tag.c - git - Git at Google

 /*
  * Builtin "git tag"
  *
  * Copyright (c) 2007 Kristian Høgsberg <krh@redhat.com>,
  *                    Carlos Rica <jasampler@gmail.com>
  * Based on git-tag.sh and mktag.c by Linus Torvalds.
  */

 #include "cache.h"
 #include "builtin.h"
 #include "refs.h"
 #include "tag.h"
 #include "run-command.h"

 static const char builtin_tag_usage[] =
   "git-tag [-n [<num>]] -l [<pattern>] | [-a | -s | -u <key-id>] [-f | -d | -v] [-m <msg> | -F <file>] <tagname> [<head>]";

 static char signingkey[1000];

 static void launch_editor(const char *path, char **buffer, unsigned long *len)
 {
 	const char *editor, *terminal;
 	struct child_process child;
 	const char *args[3];
 	int fd;

 	editor = getenv("GIT_EDITOR");
 	if (!editor && editor_program)
 		editor = editor_program;
 	if (!editor)
 		editor = getenv("VISUAL");
 	if (!editor)
 		editor = getenv("EDITOR");

 	terminal = getenv("TERM");
 	if (!editor && (!terminal || !strcmp(terminal, "dumb"))) {
 		fprintf(stderr,
 		"Terminal is dumb but no VISUAL nor EDITOR defined.\n"
 		"Please supply the message using either -m or -F option.\n");
 		exit(1);
 	}

 	if (!editor)
 		editor = "vi";

 	memset(&child, 0, sizeof(child));
 	child.argv = args;
 	args[0] = editor;
 	args[1] = path;
 	args[2] = NULL;

 	if (run_command(&child))
 		die("There was a problem with the editor %s.", editor);

 	fd = open(path, O_RDONLY);
 	if (fd < 0)
 		die("could not open '%s': %s", path, strerror(errno));
 	if (read_fd(fd, buffer, len)) {
 		free(*buffer);
 		die("could not read message file '%s': %s",
 						path, strerror(errno));
 	}
 	close(fd);
 }

 struct tag_filter {
 	const char *pattern;
 	int lines;
 };

 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"

 static int show_reference(const char *refname, const unsigned char *sha1,
 			  int flag, void *cb_data)
 {
 	struct tag_filter *filter = cb_data;

 	if (!fnmatch(filter->pattern, refname, 0)) {
 		int i;
 		unsigned long size;
 		enum object_type type;
 		char *buf, *sp, *eol;
 		size_t len;

 		if (!filter->lines) {
 			printf("%s\n", refname);
 			return 0;
 		}
 		printf("%-15s ", refname);

 		sp = buf = read_sha1_file(sha1, &type, &size);
 		if (!buf)
 			return 0;
 		if (!size) {
 			free(buf);
 			return 0;
 		}
 		/* skip header */
 		while (sp + 1 < buf + size &&
 				!(sp[0] == '\n' && sp[1] == '\n'))
 			sp++;
 		/* only take up to "lines" lines, and strip the signature */
 		for (i = 0, sp += 2;
 				i < filter->lines && sp < buf + size &&
 				prefixcmp(sp, PGP_SIGNATURE "\n");
 				i++) {
 			if (i)
 				printf("\n    ");
 			eol = memchr(sp, '\n', size - (sp - buf));
 			len = eol ? eol - sp : size - (sp - buf);
 			fwrite(sp, len, 1, stdout);
 			if (!eol)
 				break;
 			sp = eol + 1;
 		}
 		putchar('\n');
 		free(buf);
 	}

 	return 0;
 }

 static int list_tags(const char *pattern, int lines)
 {
 	struct tag_filter filter;
 	char *newpattern;

 	if (pattern == NULL)
 		pattern = "";

 	/* prepend/append * to the shell pattern: */
 	newpattern = xmalloc(strlen(pattern) + 3);
 	sprintf(newpattern, "*%s*", pattern);

 	filter.pattern = newpattern;
 	filter.lines = lines;

 	for_each_tag_ref(show_reference, (void *) &filter);

 	free(newpattern);

 	return 0;
 }

 typedef int (*each_tag_name_fn)(const char *name, const char *ref,
 				const unsigned char *sha1);

 static int for_each_tag_name(const char **argv, each_tag_name_fn fn)
 {
 	const char **p;
 	char ref[PATH_MAX];
 	int had_error = 0;
 	unsigned char sha1[20];

 	for (p = argv; *p; p++) {
 		if (snprintf(ref, sizeof(ref), "refs/tags/%s", *p)
 					>= sizeof(ref)) {
 			error("tag name too long: %.*s...", 50, *p);
 			had_error = 1;
 			continue;
 		}
 		if (!resolve_ref(ref, sha1, 1, NULL)) {
 			error("tag '%s' not found.", *p);
 			had_error = 1;
 			continue;
 		}
 		if (fn(*p, ref, sha1))
 			had_error = 1;
 	}
 	return had_error;
 }

 static int delete_tag(const char *name, const char *ref,
 				const unsigned char *sha1)
 {
 	if (delete_ref(ref, sha1))
 		return 1;
 	printf("Deleted tag '%s'\n", name);
 	return 0;
 }

 static int verify_tag(const char *name, const char *ref,
 				const unsigned char *sha1)
 {
 	const char *argv_verify_tag[] = {"git-verify-tag",
 					"-v", "SHA1_HEX", NULL};
 	argv_verify_tag[2] = sha1_to_hex(sha1);

 	if (run_command_v_opt(argv_verify_tag, 0))
 		return error("could not verify the tag '%s'", name);
 	return 0;
 }

 static ssize_t do_sign(char *buffer, size_t size, size_t max)
 {
 	struct child_process gpg;
 	const char *args[4];
 	char *bracket;
 	int len;

 	if (!*signingkey) {
 		if (strlcpy(signingkey, git_committer_info(1),
 				sizeof(signingkey)) > sizeof(signingkey) - 1)
 			return error("committer info too long.");
 		bracket = strchr(signingkey, '>');
 		if (bracket)
 			bracket[1] = '\0';
 	}

 	memset(&gpg, 0, sizeof(gpg));
 	gpg.argv = args;
 	gpg.in = -1;
 	gpg.out = -1;
 	args[0] = "gpg";
 	args[1] = "-bsau";
 	args[2] = signingkey;
 	args[3] = NULL;

 	if (start_command(&gpg))
 		return error("could not run gpg.");

 	write_or_die(gpg.in, buffer, size);
 	close(gpg.in);
 	gpg.close_in = 0;
 	len = read_in_full(gpg.out, buffer + size, max - size);

 	finish_command(&gpg);

 	if (len == max - size)
 		return error("could not read the entire signature from gpg.");

 	return size + len;
 }

 static const char tag_template[] =
 	"\n"
 	"#\n"
 	"# Write a tag message\n"
 	"#\n";

 static int git_tag_config(const char *var, const char *value)
 {
 	if (!strcmp(var, "user.signingkey")) {
 		if (!value)
 			die("user.signingkey without value");
 		if (strlcpy(signingkey, value, sizeof(signingkey))
 						>= sizeof(signingkey))
 			die("user.signingkey value too long");
 		return 0;
 	}

 	return git_default_config(var, value);
 }

 #define MAX_SIGNATURE_LENGTH 1024
 /* message must be NULL or allocated, it will be reallocated and freed */
 static void create_tag(const unsigned char *object, const char *tag,
 		       char *message, int sign, unsigned char *result)
 {
 	enum object_type type;
 	char header_buf[1024], *buffer = NULL;
 	int header_len, max_size;
 	unsigned long size = 0;

 	type = sha1_object_info(object, NULL);
 	if (type <= OBJ_NONE)
 	    die("bad object type.");

 	header_len = snprintf(header_buf, sizeof(header_buf),
 			  "object %s\n"
 			  "type %s\n"
 			  "tag %s\n"
 			  "tagger %s\n\n",
 			  sha1_to_hex(object),
 			  typename(type),
 			  tag,
 			  git_committer_info(1));

 	if (header_len > sizeof(header_buf) - 1)
 		die("tag header too big.");

 	if (!message) {
 		char *path;
 		int fd;

 		/* write the template message before editing: */
 		path = xstrdup(git_path("TAG_EDITMSG"));
 		fd = open(path, O_CREAT | O_TRUNC | O_WRONLY, 0600);
 		if (fd < 0)
 			die("could not create file '%s': %s",
 						path, strerror(errno));
 		write_or_die(fd, tag_template, strlen(tag_template));
 		close(fd);

 		launch_editor(path, &buffer, &size);

 		unlink(path);
 		free(path);
 	}
 	else {
 		buffer = message;
 		size = strlen(message);
 	}

 	size = stripspace(buffer, size, 1);

 	if (!message && !size)
 		die("no tag message?");

 	/* insert the header and add the '\n' if needed: */
 	max_size = header_len + size + (sign ? MAX_SIGNATURE_LENGTH : 0) + 1;
 	buffer = xrealloc(buffer, max_size);
 	if (size)
 		buffer[size++] = '\n';
 	memmove(buffer + header_len, buffer, size);
 	memcpy(buffer, header_buf, header_len);
 	size += header_len;

 	if (sign) {
 		size = do_sign(buffer, size, max_size);
 		if (size < 0)
 			die("unable to sign the tag");
 	}

 	if (write_sha1_file(buffer, size, tag_type, result) < 0)
 		die("unable to write tag file");
 	free(buffer);
 }

 int cmd_tag(int argc, const char **argv, const char *prefix)
 {
 	unsigned char object[20], prev[20];
 	int annotate = 0, sign = 0, force = 0, lines = 0;
 	char *message = NULL;
 	char ref[PATH_MAX];
 	const char *object_ref, *tag;
 	int i;
 	struct ref_lock *lock;

 	git_config(git_tag_config);

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

 		if (arg[0] != '-')
 			break;
 		if (!strcmp(arg, "-a")) {
 			annotate = 1;
 			continue;
 		}
 		if (!strcmp(arg, "-s")) {
 			annotate = 1;
 			sign = 1;
 			continue;
 		}
 		if (!strcmp(arg, "-f")) {
 			force = 1;
 			continue;
 		}
 		if (!strcmp(arg, "-n")) {
 			if (i + 1 == argc || *argv[i + 1] == '-')
 				/* no argument */
 				lines = 1;
 			else
 				lines = isdigit(*argv[++i]) ?
 					atoi(argv[i]) : 1;
 			continue;
 		}
 		if (!strcmp(arg, "-m")) {
 			annotate = 1;
 			i++;
 			if (i == argc)
 				die("option -m needs an argument.");
 			if (message)
 				die("only one -F or -m option is allowed.");
 			message = xstrdup(argv[i]);
 			continue;
 		}
 		if (!strcmp(arg, "-F")) {
 			unsigned long len;
 			int fd;

 			annotate = 1;
 			i++;
 			if (i == argc)
 				die("option -F needs an argument.");
 			if (message)
 				die("only one -F or -m option is allowed.");

 			if (!strcmp(argv[i], "-"))
 				fd = 0;
 			else {
 				fd = open(argv[i], O_RDONLY);
 				if (fd < 0)
 					die("could not open '%s': %s",
 						argv[i], strerror(errno));
 			}
 			len = 1024;
 			message = xmalloc(len);
 			if (read_fd(fd, &message, &len)) {
 				free(message);
 				die("cannot read %s", argv[i]);
 			}
 			continue;
 		}
 		if (!strcmp(arg, "-u")) {
 			annotate = 1;
 			sign = 1;
 			i++;
 			if (i == argc)
 				die("option -u needs an argument.");
 			if (strlcpy(signingkey, argv[i], sizeof(signingkey))
 							>= sizeof(signingkey))
 				die("argument to option -u too long");
 			continue;
 		}
 		if (!strcmp(arg, "-l"))
 			return list_tags(argv[i + 1], lines);
 		if (!strcmp(arg, "-d"))
 			return for_each_tag_name(argv + i + 1, delete_tag);
 		if (!strcmp(arg, "-v"))
 			return for_each_tag_name(argv + i + 1, verify_tag);
 		usage(builtin_tag_usage);
 	}

 	if (i == argc) {
 		if (annotate)
 			usage(builtin_tag_usage);
 		return list_tags(NULL, lines);
 	}
 	tag = argv[i++];

 	object_ref = i < argc ? argv[i] : "HEAD";
 	if (i + 1 < argc)
 		die("too many params");

 	if (get_sha1(object_ref, object))
 		die("Failed to resolve '%s' as a valid ref.", object_ref);

 	if (snprintf(ref, sizeof(ref), "refs/tags/%s", tag) > sizeof(ref) - 1)
 		die("tag name too long: %.*s...", 50, tag);
 	if (check_ref_format(ref))
 		die("'%s' is not a valid tag name.", tag);

 	if (!resolve_ref(ref, prev, 1, NULL))
 		hashclr(prev);
 	else if (!force)
 		die("tag '%s' already exists", tag);

 	if (annotate)
 		create_tag(object, tag, message, sign, object);

 	lock = lock_any_ref_for_update(ref, prev, 0);
 	if (!lock)
 		die("%s: cannot lock the ref", ref);
 	if (write_ref_sha1(lock, object, NULL) < 0)
 		die("%s: cannot update the ref", ref);

 	return 0;
 }
	/*
	* Builtin "git tag"
	*
	* Copyright (c) 2007 Kristian Høgsberg <krh@redhat.com>,
	* Carlos Rica <jasampler@gmail.com>
	* Based on git-tag.sh and mktag.c by Linus Torvalds.
	*/

	#include "cache.h"
	#include "builtin.h"
	#include "refs.h"
	#include "tag.h"
	#include "run-command.h"

	static const char builtin_tag_usage[] =
	"git-tag [-n [<num>]] -l [<pattern>] \| [-a \| -s \| -u <key-id>] [-f \| -d \| -v] [-m <msg> \| -F <file>] <tagname> [<head>]";

	static char signingkey[1000];

	static void launch_editor(const char path, char buffer, unsigned long len)
	{
	const char editor, terminal;
	struct child_process child;
	const char *args[3];
	int fd;

	editor = getenv("GIT_EDITOR");
	if (!editor && editor_program)
	editor = editor_program;
	if (!editor)
	editor = getenv("VISUAL");
	if (!editor)
	editor = getenv("EDITOR");

	terminal = getenv("TERM");
	if (!editor && (!terminal \|\| !strcmp(terminal, "dumb"))) {
	fprintf(stderr,
	"Terminal is dumb but no VISUAL nor EDITOR defined.\n"
	"Please supply the message using either -m or -F option.\n");
	exit(1);
	}

	if (!editor)
	editor = "vi";

	memset(&child, 0, sizeof(child));
	child.argv = args;
	args[0] = editor;
	args[1] = path;
	args[2] = NULL;

	if (run_command(&child))
	die("There was a problem with the editor %s.", editor);

	fd = open(path, O_RDONLY);
	if (fd < 0)
	die("could not open '%s': %s", path, strerror(errno));
	if (read_fd(fd, buffer, len)) {
	free(*buffer);
	die("could not read message file '%s': %s",
	path, strerror(errno));
	}
	close(fd);
	}

	struct tag_filter {
	const char *pattern;
	int lines;
	};

	#define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"

	static int show_reference(const char refname, const unsigned char sha1,
	int flag, void *cb_data)
	{
	struct tag_filter *filter = cb_data;

	if (!fnmatch(filter->pattern, refname, 0)) {
	int i;
	unsigned long size;
	enum object_type type;
	char buf, sp, *eol;
	size_t len;

	if (!filter->lines) {
	printf("%s\n", refname);
	return 0;
	}
	printf("%-15s ", refname);

	sp = buf = read_sha1_file(sha1, &type, &size);
	if (!buf)
	return 0;
	if (!size) {
	free(buf);
	return 0;
	}
	/* skip header */
	while (sp + 1 < buf + size &&
	!(sp[0] == '\n' && sp[1] == '\n'))
	sp++;
	/* only take up to "lines" lines, and strip the signature */
	for (i = 0, sp += 2;
	i < filter->lines && sp < buf + size &&
	prefixcmp(sp, PGP_SIGNATURE "\n");
	i++) {
	if (i)
	printf("\n ");
	eol = memchr(sp, '\n', size - (sp - buf));
	len = eol ? eol - sp : size - (sp - buf);
	fwrite(sp, len, 1, stdout);
	if (!eol)
	break;
	sp = eol + 1;
	}
	putchar('\n');
	free(buf);
	}

	return 0;
	}

	static int list_tags(const char *pattern, int lines)
	{
	struct tag_filter filter;
	char *newpattern;

	if (pattern == NULL)
	pattern = "";

	/* prepend/append * to the shell pattern: */
	newpattern = xmalloc(strlen(pattern) + 3);
	sprintf(newpattern, "%s", pattern);

	filter.pattern = newpattern;
	filter.lines = lines;

	for_each_tag_ref(show_reference, (void *) &filter);

	free(newpattern);

	return 0;
	}

	typedef int (each_tag_name_fn)(const char name, const char *ref,
	const unsigned char *sha1);

	static int for_each_tag_name(const char **argv, each_tag_name_fn fn)
	{
	const char **p;
	char ref[PATH_MAX];
	int had_error = 0;
	unsigned char sha1[20];

	for (p = argv; *p; p++) {
	if (snprintf(ref, sizeof(ref), "refs/tags/%s", *p)
	>= sizeof(ref)) {
	error("tag name too long: %.s...", 50, p);
	had_error = 1;
	continue;
	}
	if (!resolve_ref(ref, sha1, 1, NULL)) {
	error("tag '%s' not found.", *p);
	had_error = 1;
	continue;
	}
	if (fn(*p, ref, sha1))
	had_error = 1;
	}
	return had_error;
	}

	static int delete_tag(const char name, const char ref,
	const unsigned char *sha1)
	{
	if (delete_ref(ref, sha1))
	return 1;
	printf("Deleted tag '%s'\n", name);
	return 0;
	}

	static int verify_tag(const char name, const char ref,
	const unsigned char *sha1)
	{
	const char *argv_verify_tag[] = {"git-verify-tag",
	"-v", "SHA1_HEX", NULL};
	argv_verify_tag[2] = sha1_to_hex(sha1);

	if (run_command_v_opt(argv_verify_tag, 0))
	return error("could not verify the tag '%s'", name);
	return 0;
	}

	static ssize_t do_sign(char *buffer, size_t size, size_t max)
	{
	struct child_process gpg;
	const char *args[4];
	char *bracket;
	int len;

	if (!*signingkey) {
	if (strlcpy(signingkey, git_committer_info(1),
	sizeof(signingkey)) > sizeof(signingkey) - 1)
	return error("committer info too long.");
	bracket = strchr(signingkey, '>');
	if (bracket)
	bracket[1] = '\0';
	}

	memset(&gpg, 0, sizeof(gpg));
	gpg.argv = args;
	gpg.in = -1;
	gpg.out = -1;
	args[0] = "gpg";
	args[1] = "-bsau";
	args[2] = signingkey;
	args[3] = NULL;

	if (start_command(&gpg))
	return error("could not run gpg.");

	write_or_die(gpg.in, buffer, size);
	close(gpg.in);
	gpg.close_in = 0;
	len = read_in_full(gpg.out, buffer + size, max - size);

	finish_command(&gpg);

	if (len == max - size)
	return error("could not read the entire signature from gpg.");

	return size + len;
	}

	static const char tag_template[] =
	"\n"
	"#\n"
	"# Write a tag message\n"
	"#\n";

	static int git_tag_config(const char var, const char value)
	{
	if (!strcmp(var, "user.signingkey")) {
	if (!value)
	die("user.signingkey without value");
	if (strlcpy(signingkey, value, sizeof(signingkey))
	>= sizeof(signingkey))
	die("user.signingkey value too long");
	return 0;
	}

	return git_default_config(var, value);
	}

	#define MAX_SIGNATURE_LENGTH 1024
	/* message must be NULL or allocated, it will be reallocated and freed */
	static void create_tag(const unsigned char object, const char tag,
	char message, int sign, unsigned char result)
	{
	enum object_type type;
	char header_buf[1024], *buffer = NULL;
	int header_len, max_size;
	unsigned long size = 0;

	type = sha1_object_info(object, NULL);
	if (type <= OBJ_NONE)
	die("bad object type.");

	header_len = snprintf(header_buf, sizeof(header_buf),
	"object %s\n"
	"type %s\n"
	"tag %s\n"
	"tagger %s\n\n",
	sha1_to_hex(object),
	typename(type),
	tag,
	git_committer_info(1));

	if (header_len > sizeof(header_buf) - 1)
	die("tag header too big.");

	if (!message) {
	char *path;
	int fd;

	/* write the template message before editing: */
	path = xstrdup(git_path("TAG_EDITMSG"));
	fd = open(path, O_CREAT \| O_TRUNC \| O_WRONLY, 0600);
	if (fd < 0)
	die("could not create file '%s': %s",
	path, strerror(errno));
	write_or_die(fd, tag_template, strlen(tag_template));
	close(fd);

	launch_editor(path, &buffer, &size);

	unlink(path);
	free(path);
	}
	else {
	buffer = message;
	size = strlen(message);
	}

	size = stripspace(buffer, size, 1);

	if (!message && !size)
	die("no tag message?");

	/* insert the header and add the '\n' if needed: */
	max_size = header_len + size + (sign ? MAX_SIGNATURE_LENGTH : 0) + 1;
	buffer = xrealloc(buffer, max_size);
	if (size)
	buffer[size++] = '\n';
	memmove(buffer + header_len, buffer, size);
	memcpy(buffer, header_buf, header_len);
	size += header_len;

	if (sign) {
	size = do_sign(buffer, size, max_size);
	if (size < 0)
	die("unable to sign the tag");
	}

	if (write_sha1_file(buffer, size, tag_type, result) < 0)
	die("unable to write tag file");
	free(buffer);
	}

	int cmd_tag(int argc, const char *argv, const char prefix)
	{
	unsigned char object[20], prev[20];
	int annotate = 0, sign = 0, force = 0, lines = 0;
	char *message = NULL;
	char ref[PATH_MAX];
	const char object_ref, tag;
	int i;
	struct ref_lock *lock;

	git_config(git_tag_config);

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

	if (arg[0] != '-')
	break;
	if (!strcmp(arg, "-a")) {
	annotate = 1;
	continue;
	}
	if (!strcmp(arg, "-s")) {
	annotate = 1;
	sign = 1;
	continue;
	}
	if (!strcmp(arg, "-f")) {
	force = 1;
	continue;
	}
	if (!strcmp(arg, "-n")) {
	if (i + 1 == argc \|\| *argv[i + 1] == '-')
	/* no argument */
	lines = 1;
	else
	lines = isdigit(*argv[++i]) ?
	atoi(argv[i]) : 1;
	continue;
	}
	if (!strcmp(arg, "-m")) {
	annotate = 1;
	i++;
	if (i == argc)
	die("option -m needs an argument.");
	if (message)
	die("only one -F or -m option is allowed.");
	message = xstrdup(argv[i]);
	continue;
	}
	if (!strcmp(arg, "-F")) {
	unsigned long len;
	int fd;

	annotate = 1;
	i++;
	if (i == argc)
	die("option -F needs an argument.");
	if (message)
	die("only one -F or -m option is allowed.");

	if (!strcmp(argv[i], "-"))
	fd = 0;
	else {
	fd = open(argv[i], O_RDONLY);
	if (fd < 0)
	die("could not open '%s': %s",
	argv[i], strerror(errno));
	}
	len = 1024;
	message = xmalloc(len);
	if (read_fd(fd, &message, &len)) {
	free(message);
	die("cannot read %s", argv[i]);
	}
	continue;
	}
	if (!strcmp(arg, "-u")) {
	annotate = 1;
	sign = 1;
	i++;
	if (i == argc)
	die("option -u needs an argument.");
	if (strlcpy(signingkey, argv[i], sizeof(signingkey))
	>= sizeof(signingkey))
	die("argument to option -u too long");
	continue;
	}
	if (!strcmp(arg, "-l"))
	return list_tags(argv[i + 1], lines);
	if (!strcmp(arg, "-d"))
	return for_each_tag_name(argv + i + 1, delete_tag);
	if (!strcmp(arg, "-v"))
	return for_each_tag_name(argv + i + 1, verify_tag);
	usage(builtin_tag_usage);
	}

	if (i == argc) {
	if (annotate)
	usage(builtin_tag_usage);
	return list_tags(NULL, lines);
	}
	tag = argv[i++];

	object_ref = i < argc ? argv[i] : "HEAD";
	if (i + 1 < argc)
	die("too many params");

	if (get_sha1(object_ref, object))
	die("Failed to resolve '%s' as a valid ref.", object_ref);

	if (snprintf(ref, sizeof(ref), "refs/tags/%s", tag) > sizeof(ref) - 1)
	die("tag name too long: %.*s...", 50, tag);
	if (check_ref_format(ref))
	die("'%s' is not a valid tag name.", tag);

	if (!resolve_ref(ref, prev, 1, NULL))
	hashclr(prev);
	else if (!force)
	die("tag '%s' already exists", tag);

	if (annotate)
	create_tag(object, tag, message, sign, object);

	lock = lock_any_ref_for_update(ref, prev, 0);
	if (!lock)
	die("%s: cannot lock the ref", ref);
	if (write_ref_sha1(lock, object, NULL) < 0)
	die("%s: cannot update the ref", ref);

	return 0;
	}