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"
 #include "parse-options.h"

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

 static char signingkey[1000];

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

 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->with_commit) {
 			struct commit *commit;

 			commit = lookup_commit_reference_gently(sha1, 1);
 			if (!commit)
 				return 0;
 			if (!is_descendant_of(commit, filter->with_commit))
 				return 0;
 		}

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

 		buf = read_sha1_file(sha1, &type, &size);
 		if (!buf || !size)
 			return 0;

 		/* skip header */
 		sp = strstr(buf, "\n\n");
 		if (!sp) {
 			free(buf);
 			return 0;
 		}
 		/* only take up to "lines" lines, and strip the signature */
 		size = parse_signature(buf, size);
 		for (i = 0, sp += 2;
 				i < filter->lines && sp < buf + size;
 				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 commit_list *with_commit)
 {
 	struct tag_filter filter;

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

 	filter.pattern = pattern;
 	filter.lines = lines;
 	filter.with_commit = with_commit;

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

 	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, 0))
 		return 1;
 	printf(_("Deleted tag '%s' (was %s)\n"), name, find_unique_abbrev(sha1, DEFAULT_ABBREV));
 	return 0;
 }

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

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

 static int do_sign(struct strbuf *buffer)
 {
 	struct child_process gpg;
 	const char *args[4];
 	char *bracket;
 	int len;
 	int i, j;

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

 	/* When the username signingkey is bad, program could be terminated
 	 * because gpg exits without reading and then write gets SIGPIPE. */
 	signal(SIGPIPE, SIG_IGN);

 	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."));

 	if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
 		close(gpg.in);
 		close(gpg.out);
 		finish_command(&gpg);
 		return error(_("gpg did not accept the tag data"));
 	}
 	close(gpg.in);
 	len = strbuf_read(buffer, gpg.out, 1024);
 	close(gpg.out);

 	if (finish_command(&gpg) || !len || len < 0)
 		return error(_("gpg failed to sign the tag"));

 	/* Strip CR from the line endings, in case we are on Windows. */
 	for (i = j = 0; i < buffer->len; i++)
 		if (buffer->buf[i] != '\r') {
 			if (i != j)
 				buffer->buf[j] = buffer->buf[i];
 			j++;
 		}
 	strbuf_setlen(buffer, j);

 	return 0;
 }

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

 static void set_signingkey(const char *value)
 {
 	if (strlcpy(signingkey, value, sizeof(signingkey)) >= sizeof(signingkey))
 		die(_("signing key value too long (%.10s...)"), value);
 }

 static int git_tag_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "user.signingkey")) {
 		if (!value)
 			return config_error_nonbool(var);
 		set_signingkey(value);
 		return 0;
 	}

 	return git_default_config(var, value, cb);
 }

 static void write_tag_body(int fd, const unsigned char *sha1)
 {
 	unsigned long size;
 	enum object_type type;
 	char *buf, *sp;

 	buf = read_sha1_file(sha1, &type, &size);
 	if (!buf)
 		return;
 	/* skip header */
 	sp = strstr(buf, "\n\n");

 	if (!sp || !size || type != OBJ_TAG) {
 		free(buf);
 		return;
 	}
 	sp += 2; /* skip the 2 LFs */
 	write_or_die(fd, sp, parse_signature(sp, buf + size - sp));

 	free(buf);
 }

 static int build_tag_object(struct strbuf *buf, int sign, unsigned char *result)
 {
 	if (sign && do_sign(buf) < 0)
 		return error(_("unable to sign the tag"));
 	if (write_sha1_file(buf->buf, buf->len, tag_type, result) < 0)
 		return error(_("unable to write tag file"));
 	return 0;
 }

 static void create_tag(const unsigned char *object, const char *tag,
 		       struct strbuf *buf, int message, int sign,
 		       unsigned char *prev, unsigned char *result)
 {
 	enum object_type type;
 	char header_buf[1024];
 	int header_len;
 	char *path = NULL;

 	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(IDENT_ERROR_ON_NO_NAME));

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

 	if (!message) {
 		int fd;

 		/* write the template message before editing: */
 		path = git_pathdup("TAG_EDITMSG");
 		fd = open(path, O_CREAT | O_TRUNC | O_WRONLY, 0600);
 		if (fd < 0)
 			die_errno(_("could not create file '%s'"), path);

 		if (!is_null_sha1(prev))
 			write_tag_body(fd, prev);
 		else
 			write_or_die(fd, _(tag_template), strlen(_(tag_template)));
 		close(fd);

 		if (launch_editor(path, buf, NULL)) {
 			fprintf(stderr,
 			_("Please supply the message using either -m or -F option.\n"));
 			exit(1);
 		}
 	}

 	stripspace(buf, 1);

 	if (!message && !buf->len)
 		die(_("no tag message?"));

 	strbuf_insert(buf, 0, header_buf, header_len);

 	if (build_tag_object(buf, sign, result) < 0) {
 		if (path)
 			fprintf(stderr, _("The tag message has been left in %s\n"),
 				path);
 		exit(128);
 	}
 	if (path) {
 		unlink_or_warn(path);
 		free(path);
 	}
 }

 struct msg_arg {
 	int given;
 	struct strbuf buf;
 };

 static int parse_msg_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct msg_arg *msg = opt->value;

 	if (!arg)
 		return -1;
 	if (msg->buf.len)
 		strbuf_addstr(&(msg->buf), "\n\n");
 	strbuf_addstr(&(msg->buf), arg);
 	msg->given = 1;
 	return 0;
 }

 static int strbuf_check_tag_ref(struct strbuf *sb, const char *name)
 {
 	if (name[0] == '-')
 		return CHECK_REF_FORMAT_ERROR;

 	strbuf_reset(sb);
 	strbuf_addf(sb, "refs/tags/%s", name);

 	return check_ref_format(sb->buf);
 }

 int cmd_tag(int argc, const char **argv, const char *prefix)
 {
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf ref = STRBUF_INIT;
 	unsigned char object[20], prev[20];
 	const char *object_ref, *tag;
 	struct ref_lock *lock;

 	int annotate = 0, sign = 0, force = 0, lines = -1,
 		list = 0, delete = 0, verify = 0;
 	const char *msgfile = NULL, *keyid = NULL;
 	struct msg_arg msg = { 0, STRBUF_INIT };
 	struct commit_list *with_commit = NULL;
 	struct option options[] = {
 		OPT_BOOLEAN('l', NULL, &list, "list tag names"),
 		{ OPTION_INTEGER, 'n', NULL, &lines, "n",
 				"print <n> lines of each tag message",
 				PARSE_OPT_OPTARG, NULL, 1 },
 		OPT_BOOLEAN('d', NULL, &delete, "delete tags"),
 		OPT_BOOLEAN('v', NULL, &verify, "verify tags"),

 		OPT_GROUP("Tag creation options"),
 		OPT_BOOLEAN('a', NULL, &annotate,
 					"annotated tag, needs a message"),
 		OPT_CALLBACK('m', NULL, &msg, "message",
 			     "tag message", parse_msg_arg),
 		OPT_FILENAME('F', NULL, &msgfile, "read message from file"),
 		OPT_BOOLEAN('s', NULL, &sign, "annotated and GPG-signed tag"),
 		OPT_STRING('u', NULL, &keyid, "key-id",
 					"use another key to sign the tag"),
 		OPT__FORCE(&force, "replace the tag if exists"),

 		OPT_GROUP("Tag listing options"),
 		{
 			OPTION_CALLBACK, 0, "contains", &with_commit, "commit",
 			"print only tags that contain the commit",
 			PARSE_OPT_LASTARG_DEFAULT,
 			parse_opt_with_commit, (intptr_t)"HEAD",
 		},
 		OPT_END()
 	};

 	git_config(git_tag_config, NULL);

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

 	if (keyid) {
 		sign = 1;
 		set_signingkey(keyid);
 	}
 	if (sign)
 		annotate = 1;
 	if (argc == 0 && !(delete || verify))
 		list = 1;

 	if ((annotate || msg.given || msgfile || force) &&
 	    (list || delete || verify))
 		usage_with_options(git_tag_usage, options);

 	if (list + delete + verify > 1)
 		usage_with_options(git_tag_usage, options);
 	if (list)
 		return list_tags(argv[0], lines == -1 ? 0 : lines,
 				 with_commit);
 	if (lines != -1)
 		die(_("-n option is only allowed with -l."));
 	if (with_commit)
 		die(_("--contains option is only allowed with -l."));
 	if (delete)
 		return for_each_tag_name(argv, delete_tag);
 	if (verify)
 		return for_each_tag_name(argv, verify_tag);

 	if (msg.given || msgfile) {
 		if (msg.given && msgfile)
 			die(_("only one -F or -m option is allowed."));
 		annotate = 1;
 		if (msg.given)
 			strbuf_addbuf(&buf, &(msg.buf));
 		else {
 			if (!strcmp(msgfile, "-")) {
 				if (strbuf_read(&buf, 0, 1024) < 0)
 					die_errno(_("cannot read '%s'"), msgfile);
 			} else {
 				if (strbuf_read_file(&buf, msgfile, 1024) < 0)
 					die_errno(_("could not open or read '%s'"),
 						msgfile);
 			}
 		}
 	}

 	tag = argv[0];

 	object_ref = argc == 2 ? argv[1] : "HEAD";
 	if (argc > 2)
 		die(_("too many params"));

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

 	if (strbuf_check_tag_ref(&ref, tag))
 		die(_("'%s' is not a valid tag name."), tag);

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

 	if (annotate)
 		create_tag(object, tag, &buf, msg.given || msgfile,
 			   sign, prev, object);

 	lock = lock_any_ref_for_update(ref.buf, prev, 0);
 	if (!lock)
 		die(_("%s: cannot lock the ref"), ref.buf);
 	if (write_ref_sha1(lock, object, NULL) < 0)
 		die(_("%s: cannot update the ref"), ref.buf);
 	if (force && hashcmp(prev, object))
 		printf(_("Updated tag '%s' (was %s)\n"), tag, find_unique_abbrev(prev, DEFAULT_ABBREV));

 	strbuf_release(&buf);
 	strbuf_release(&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"
	#include "parse-options.h"

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

	static char signingkey[1000];

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

	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->with_commit) {
	struct commit *commit;

	commit = lookup_commit_reference_gently(sha1, 1);
	if (!commit)
	return 0;
	if (!is_descendant_of(commit, filter->with_commit))
	return 0;
	}

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

	buf = read_sha1_file(sha1, &type, &size);
	if (!buf \|\| !size)
	return 0;

	/* skip header */
	sp = strstr(buf, "\n\n");
	if (!sp) {
	free(buf);
	return 0;
	}
	/* only take up to "lines" lines, and strip the signature */
	size = parse_signature(buf, size);
	for (i = 0, sp += 2;
	i < filter->lines && sp < buf + size;
	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 commit_list *with_commit)
	{
	struct tag_filter filter;

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

	filter.pattern = pattern;
	filter.lines = lines;
	filter.with_commit = with_commit;

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

	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, 0))
	return 1;
	printf(_("Deleted tag '%s' (was %s)\n"), name, find_unique_abbrev(sha1, DEFAULT_ABBREV));
	return 0;
	}

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

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

	static int do_sign(struct strbuf *buffer)
	{
	struct child_process gpg;
	const char *args[4];
	char *bracket;
	int len;
	int i, j;

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

	/* When the username signingkey is bad, program could be terminated
	* because gpg exits without reading and then write gets SIGPIPE. */
	signal(SIGPIPE, SIG_IGN);

	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."));

	if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
	close(gpg.in);
	close(gpg.out);
	finish_command(&gpg);
	return error(_("gpg did not accept the tag data"));
	}
	close(gpg.in);
	len = strbuf_read(buffer, gpg.out, 1024);
	close(gpg.out);

	if (finish_command(&gpg) \|\| !len \|\| len < 0)
	return error(_("gpg failed to sign the tag"));

	/* Strip CR from the line endings, in case we are on Windows. */
	for (i = j = 0; i < buffer->len; i++)
	if (buffer->buf[i] != '\r') {
	if (i != j)
	buffer->buf[j] = buffer->buf[i];
	j++;
	}
	strbuf_setlen(buffer, j);

	return 0;
	}

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

	static void set_signingkey(const char *value)
	{
	if (strlcpy(signingkey, value, sizeof(signingkey)) >= sizeof(signingkey))
	die(_("signing key value too long (%.10s...)"), value);
	}

	static int git_tag_config(const char var, const char value, void *cb)
	{
	if (!strcmp(var, "user.signingkey")) {
	if (!value)
	return config_error_nonbool(var);
	set_signingkey(value);
	return 0;
	}

	return git_default_config(var, value, cb);
	}

	static void write_tag_body(int fd, const unsigned char *sha1)
	{
	unsigned long size;
	enum object_type type;
	char buf, sp;

	buf = read_sha1_file(sha1, &type, &size);
	if (!buf)
	return;
	/* skip header */
	sp = strstr(buf, "\n\n");

	if (!sp \|\| !size \|\| type != OBJ_TAG) {
	free(buf);
	return;
	}
	sp += 2; /* skip the 2 LFs */
	write_or_die(fd, sp, parse_signature(sp, buf + size - sp));

	free(buf);
	}

	static int build_tag_object(struct strbuf buf, int sign, unsigned char result)
	{
	if (sign && do_sign(buf) < 0)
	return error(_("unable to sign the tag"));
	if (write_sha1_file(buf->buf, buf->len, tag_type, result) < 0)
	return error(_("unable to write tag file"));
	return 0;
	}

	static void create_tag(const unsigned char object, const char tag,
	struct strbuf *buf, int message, int sign,
	unsigned char prev, unsigned char result)
	{
	enum object_type type;
	char header_buf[1024];
	int header_len;
	char *path = NULL;

	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(IDENT_ERROR_ON_NO_NAME));

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

	if (!message) {
	int fd;

	/* write the template message before editing: */
	path = git_pathdup("TAG_EDITMSG");
	fd = open(path, O_CREAT \| O_TRUNC \| O_WRONLY, 0600);
	if (fd < 0)
	die_errno(_("could not create file '%s'"), path);

	if (!is_null_sha1(prev))
	write_tag_body(fd, prev);
	else
	write_or_die(fd, _(tag_template), strlen(_(tag_template)));
	close(fd);

	if (launch_editor(path, buf, NULL)) {
	fprintf(stderr,
	_("Please supply the message using either -m or -F option.\n"));
	exit(1);
	}
	}

	stripspace(buf, 1);

	if (!message && !buf->len)
	die(_("no tag message?"));

	strbuf_insert(buf, 0, header_buf, header_len);

	if (build_tag_object(buf, sign, result) < 0) {
	if (path)
	fprintf(stderr, _("The tag message has been left in %s\n"),
	path);
	exit(128);
	}
	if (path) {
	unlink_or_warn(path);
	free(path);
	}
	}

	struct msg_arg {
	int given;
	struct strbuf buf;
	};

	static int parse_msg_arg(const struct option opt, const char arg, int unset)
	{
	struct msg_arg *msg = opt->value;

	if (!arg)
	return -1;
	if (msg->buf.len)
	strbuf_addstr(&(msg->buf), "\n\n");
	strbuf_addstr(&(msg->buf), arg);
	msg->given = 1;
	return 0;
	}

	static int strbuf_check_tag_ref(struct strbuf sb, const char name)
	{
	if (name[0] == '-')
	return CHECK_REF_FORMAT_ERROR;

	strbuf_reset(sb);
	strbuf_addf(sb, "refs/tags/%s", name);

	return check_ref_format(sb->buf);
	}

	int cmd_tag(int argc, const char *argv, const char prefix)
	{
	struct strbuf buf = STRBUF_INIT;
	struct strbuf ref = STRBUF_INIT;
	unsigned char object[20], prev[20];
	const char object_ref, tag;
	struct ref_lock *lock;

	int annotate = 0, sign = 0, force = 0, lines = -1,
	list = 0, delete = 0, verify = 0;
	const char msgfile = NULL, keyid = NULL;
	struct msg_arg msg = { 0, STRBUF_INIT };
	struct commit_list *with_commit = NULL;
	struct option options[] = {
	OPT_BOOLEAN('l', NULL, &list, "list tag names"),
	{ OPTION_INTEGER, 'n', NULL, &lines, "n",
	"print <n> lines of each tag message",
	PARSE_OPT_OPTARG, NULL, 1 },
	OPT_BOOLEAN('d', NULL, &delete, "delete tags"),
	OPT_BOOLEAN('v', NULL, &verify, "verify tags"),

	OPT_GROUP("Tag creation options"),
	OPT_BOOLEAN('a', NULL, &annotate,
	"annotated tag, needs a message"),
	OPT_CALLBACK('m', NULL, &msg, "message",
	"tag message", parse_msg_arg),
	OPT_FILENAME('F', NULL, &msgfile, "read message from file"),
	OPT_BOOLEAN('s', NULL, &sign, "annotated and GPG-signed tag"),
	OPT_STRING('u', NULL, &keyid, "key-id",
	"use another key to sign the tag"),
	OPT__FORCE(&force, "replace the tag if exists"),

	OPT_GROUP("Tag listing options"),
	{
	OPTION_CALLBACK, 0, "contains", &with_commit, "commit",
	"print only tags that contain the commit",
	PARSE_OPT_LASTARG_DEFAULT,
	parse_opt_with_commit, (intptr_t)"HEAD",
	},
	OPT_END()
	};

	git_config(git_tag_config, NULL);

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

	if (keyid) {
	sign = 1;
	set_signingkey(keyid);
	}
	if (sign)
	annotate = 1;
	if (argc == 0 && !(delete \|\| verify))
	list = 1;

	if ((annotate \|\| msg.given \|\| msgfile \|\| force) &&
	(list \|\| delete \|\| verify))
	usage_with_options(git_tag_usage, options);

	if (list + delete + verify > 1)
	usage_with_options(git_tag_usage, options);
	if (list)
	return list_tags(argv[0], lines == -1 ? 0 : lines,
	with_commit);
	if (lines != -1)
	die(_("-n option is only allowed with -l."));
	if (with_commit)
	die(_("--contains option is only allowed with -l."));
	if (delete)
	return for_each_tag_name(argv, delete_tag);
	if (verify)
	return for_each_tag_name(argv, verify_tag);

	if (msg.given \|\| msgfile) {
	if (msg.given && msgfile)
	die(_("only one -F or -m option is allowed."));
	annotate = 1;
	if (msg.given)
	strbuf_addbuf(&buf, &(msg.buf));
	else {
	if (!strcmp(msgfile, "-")) {
	if (strbuf_read(&buf, 0, 1024) < 0)
	die_errno(_("cannot read '%s'"), msgfile);
	} else {
	if (strbuf_read_file(&buf, msgfile, 1024) < 0)
	die_errno(_("could not open or read '%s'"),
	msgfile);
	}
	}
	}

	tag = argv[0];

	object_ref = argc == 2 ? argv[1] : "HEAD";
	if (argc > 2)
	die(_("too many params"));

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

	if (strbuf_check_tag_ref(&ref, tag))
	die(_("'%s' is not a valid tag name."), tag);

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

	if (annotate)
	create_tag(object, tag, &buf, msg.given \|\| msgfile,
	sign, prev, object);

	lock = lock_any_ref_for_update(ref.buf, prev, 0);
	if (!lock)
	die(_("%s: cannot lock the ref"), ref.buf);
	if (write_ref_sha1(lock, object, NULL) < 0)
	die(_("%s: cannot update the ref"), ref.buf);
	if (force && hashcmp(prev, object))
	printf(_("Updated tag '%s' (was %s)\n"), tag, find_unique_abbrev(prev, DEFAULT_ABBREV));

	strbuf_release(&buf);
	strbuf_release(&ref);
	return 0;
	}