builtin/help.c - jrn/git - Git at Google

 /*
  * Builtin help command
  */
 #include "cache.h"
 #include "builtin.h"
 #include "exec_cmd.h"
 #include "parse-options.h"
 #include "run-command.h"
 #include "column.h"
 #include "help.h"

 #ifndef DEFAULT_HELP_FORMAT
 #define DEFAULT_HELP_FORMAT "man"
 #endif

 static struct man_viewer_list {
 	struct man_viewer_list *next;
 	char name[FLEX_ARRAY];
 } *man_viewer_list;

 static struct man_viewer_info_list {
 	struct man_viewer_info_list *next;
 	const char *info;
 	char name[FLEX_ARRAY];
 } *man_viewer_info_list;

 enum help_format {
 	HELP_FORMAT_NONE,
 	HELP_FORMAT_MAN,
 	HELP_FORMAT_INFO,
 	HELP_FORMAT_WEB
 };

 static const char *html_path;

 static int show_all = 0;
 static int show_guides = 0;
 static unsigned int colopts;
 static enum help_format help_format = HELP_FORMAT_NONE;
 static struct option builtin_help_options[] = {
 	OPT_BOOL('a', "all", &show_all, N_("print all available commands")),
 	OPT_BOOL('g', "guides", &show_guides, N_("print list of useful guides")),
 	OPT_SET_INT('m', "man", &help_format, N_("show man page"), HELP_FORMAT_MAN),
 	OPT_SET_INT('w', "web", &help_format, N_("show manual in web browser"),
 			HELP_FORMAT_WEB),
 	OPT_SET_INT('i', "info", &help_format, N_("show info page"),
 			HELP_FORMAT_INFO),
 	OPT_END(),
 };

 static const char * const builtin_help_usage[] = {
 	N_("git help [--all] [--guides] [--man | --web | --info] [<command>]"),
 	NULL
 };

 static enum help_format parse_help_format(const char *format)
 {
 	if (!strcmp(format, "man"))
 		return HELP_FORMAT_MAN;
 	if (!strcmp(format, "info"))
 		return HELP_FORMAT_INFO;
 	if (!strcmp(format, "web") || !strcmp(format, "html"))
 		return HELP_FORMAT_WEB;
 	die(_("unrecognized help format '%s'"), format);
 }

 static const char *get_man_viewer_info(const char *name)
 {
 	struct man_viewer_info_list *viewer;

 	for (viewer = man_viewer_info_list; viewer; viewer = viewer->next)
 	{
 		if (!strcasecmp(name, viewer->name))
 			return viewer->info;
 	}
 	return NULL;
 }

 static int check_emacsclient_version(void)
 {
 	struct strbuf buffer = STRBUF_INIT;
 	struct child_process ec_process = CHILD_PROCESS_INIT;
 	const char *argv_ec[] = { "emacsclient", "--version", NULL };
 	int version;

 	/* emacsclient prints its version number on stderr */
 	ec_process.argv = argv_ec;
 	ec_process.err = -1;
 	ec_process.stdout_to_stderr = 1;
 	if (start_command(&ec_process))
 		return error(_("Failed to start emacsclient."));

 	strbuf_read(&buffer, ec_process.err, 20);
 	close(ec_process.err);

 	/*
 	 * Don't bother checking return value, because "emacsclient --version"
 	 * seems to always exits with code 1.
 	 */
 	finish_command(&ec_process);

 	if (!starts_with(buffer.buf, "emacsclient")) {
 		strbuf_release(&buffer);
 		return error(_("Failed to parse emacsclient version."));
 	}

 	strbuf_remove(&buffer, 0, strlen("emacsclient"));
 	version = atoi(buffer.buf);

 	if (version < 22) {
 		strbuf_release(&buffer);
 		return error(_("emacsclient version '%d' too old (< 22)."),
 			version);
 	}

 	strbuf_release(&buffer);
 	return 0;
 }

 static void exec_woman_emacs(const char *path, const char *page)
 {
 	if (!check_emacsclient_version()) {
 		/* This works only with emacsclient version >= 22. */
 		struct strbuf man_page = STRBUF_INIT;

 		if (!path)
 			path = "emacsclient";
 		strbuf_addf(&man_page, "(woman \"%s\")", page);
 		execlp(path, "emacsclient", "-e", man_page.buf, (char *)NULL);
 		warning(_("failed to exec '%s': %s"), path, strerror(errno));
 	}
 }

 static void exec_man_konqueror(const char *path, const char *page)
 {
 	const char *display = getenv("DISPLAY");
 	if (display && *display) {
 		struct strbuf man_page = STRBUF_INIT;
 		const char *filename = "kfmclient";

 		/* It's simpler to launch konqueror using kfmclient. */
 		if (path) {
 			const char *file = strrchr(path, '/');
 			if (file && !strcmp(file + 1, "konqueror")) {
 				char *new = xstrdup(path);
 				char *dest = strrchr(new, '/');

 				/* strlen("konqueror") == strlen("kfmclient") */
 				strcpy(dest + 1, "kfmclient");
 				path = new;
 			}
 			if (file)
 				filename = file;
 		} else
 			path = "kfmclient";
 		strbuf_addf(&man_page, "man:%s(1)", page);
 		execlp(path, filename, "newTab", man_page.buf, (char *)NULL);
 		warning(_("failed to exec '%s': %s"), path, strerror(errno));
 	}
 }

 static void exec_man_man(const char *path, const char *page)
 {
 	if (!path)
 		path = "man";
 	execlp(path, "man", page, (char *)NULL);
 	warning(_("failed to exec '%s': %s"), path, strerror(errno));
 }

 static void exec_man_cmd(const char *cmd, const char *page)
 {
 	struct strbuf shell_cmd = STRBUF_INIT;
 	strbuf_addf(&shell_cmd, "%s %s", cmd, page);
 	execl(SHELL_PATH, SHELL_PATH, "-c", shell_cmd.buf, (char *)NULL);
 	warning(_("failed to exec '%s': %s"), cmd, strerror(errno));
 }

 static void add_man_viewer(const char *name)
 {
 	struct man_viewer_list **p = &man_viewer_list;
 	size_t len = strlen(name);

 	while (*p)
 		p = &((*p)->next);
 	*p = xcalloc(1, (sizeof(**p) + len + 1));
 	strncpy((*p)->name, name, len);
 }

 static int supported_man_viewer(const char *name, size_t len)
 {
 	return (!strncasecmp("man", name, len) ||
 		!strncasecmp("woman", name, len) ||
 		!strncasecmp("konqueror", name, len));
 }

 static void do_add_man_viewer_info(const char *name,
 				   size_t len,
 				   const char *value)
 {
 	struct man_viewer_info_list *new = xcalloc(1, sizeof(*new) + len + 1);

 	strncpy(new->name, name, len);
 	new->info = xstrdup(value);
 	new->next = man_viewer_info_list;
 	man_viewer_info_list = new;
 }

 static int add_man_viewer_path(const char *name,
 			       size_t len,
 			       const char *value)
 {
 	if (supported_man_viewer(name, len))
 		do_add_man_viewer_info(name, len, value);
 	else
 		warning(_("'%s': path for unsupported man viewer.\n"
 			  "Please consider using 'man.<tool>.cmd' instead."),
 			name);

 	return 0;
 }

 static int add_man_viewer_cmd(const char *name,
 			      size_t len,
 			      const char *value)
 {
 	if (supported_man_viewer(name, len))
 		warning(_("'%s': cmd for supported man viewer.\n"
 			  "Please consider using 'man.<tool>.path' instead."),
 			name);
 	else
 		do_add_man_viewer_info(name, len, value);

 	return 0;
 }

 static int add_man_viewer_info(const char *var, const char *value)
 {
 	const char *name, *subkey;
 	int namelen;

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

 	if (!strcmp(subkey, "path")) {
 		if (!value)
 			return config_error_nonbool(var);
 		return add_man_viewer_path(name, namelen, value);
 	}
 	if (!strcmp(subkey, "cmd")) {
 		if (!value)
 			return config_error_nonbool(var);
 		return add_man_viewer_cmd(name, namelen, value);
 	}

 	return 0;
 }

 static int git_help_config(const char *var, const char *value, void *cb)
 {
 	if (starts_with(var, "column."))
 		return git_column_config(var, value, "help", &colopts);
 	if (!strcmp(var, "help.format")) {
 		if (!value)
 			return config_error_nonbool(var);
 		help_format = parse_help_format(value);
 		return 0;
 	}
 	if (!strcmp(var, "help.htmlpath")) {
 		if (!value)
 			return config_error_nonbool(var);
 		html_path = xstrdup(value);
 		return 0;
 	}
 	if (!strcmp(var, "man.viewer")) {
 		if (!value)
 			return config_error_nonbool(var);
 		add_man_viewer(value);
 		return 0;
 	}
 	if (starts_with(var, "man."))
 		return add_man_viewer_info(var, value);

 	return git_default_config(var, value, cb);
 }

 static struct cmdnames main_cmds, other_cmds;

 static int is_git_command(const char *s)
 {
 	if (is_builtin(s))
 		return 1;

 	load_command_list("git-", &main_cmds, &other_cmds);
 	return is_in_cmdlist(&main_cmds, s) ||
 		is_in_cmdlist(&other_cmds, s);
 }

 static const char *prepend(const char *prefix, const char *cmd)
 {
 	size_t pre_len = strlen(prefix);
 	size_t cmd_len = strlen(cmd);
 	char *p = xmalloc(pre_len + cmd_len + 1);
 	memcpy(p, prefix, pre_len);
 	strcpy(p + pre_len, cmd);
 	return p;
 }

 static const char *cmd_to_page(const char *git_cmd)
 {
 	if (!git_cmd)
 		return "git";
 	else if (starts_with(git_cmd, "git"))
 		return git_cmd;
 	else if (is_git_command(git_cmd))
 		return prepend("git-", git_cmd);
 	else
 		return prepend("git", git_cmd);
 }

 static void setup_man_path(void)
 {
 	struct strbuf new_path = STRBUF_INIT;
 	const char *old_path = getenv("MANPATH");
 	char *git_man_path = system_path(GIT_MAN_PATH);

 	/* We should always put ':' after our path. If there is no
 	 * old_path, the ':' at the end will let 'man' to try
 	 * system-wide paths after ours to find the manual page. If
 	 * there is old_path, we need ':' as delimiter. */
 	strbuf_addstr(&new_path, git_man_path);
 	strbuf_addch(&new_path, ':');
 	if (old_path)
 		strbuf_addstr(&new_path, old_path);

 	free(git_man_path);
 	setenv("MANPATH", new_path.buf, 1);

 	strbuf_release(&new_path);
 }

 static void exec_viewer(const char *name, const char *page)
 {
 	const char *info = get_man_viewer_info(name);

 	if (!strcasecmp(name, "man"))
 		exec_man_man(info, page);
 	else if (!strcasecmp(name, "woman"))
 		exec_woman_emacs(info, page);
 	else if (!strcasecmp(name, "konqueror"))
 		exec_man_konqueror(info, page);
 	else if (info)
 		exec_man_cmd(info, page);
 	else
 		warning(_("'%s': unknown man viewer."), name);
 }

 static void show_man_page(const char *git_cmd)
 {
 	struct man_viewer_list *viewer;
 	const char *page = cmd_to_page(git_cmd);
 	const char *fallback = getenv("GIT_MAN_VIEWER");

 	setup_man_path();
 	for (viewer = man_viewer_list; viewer; viewer = viewer->next)
 	{
 		exec_viewer(viewer->name, page); /* will return when unable */
 	}
 	if (fallback)
 		exec_viewer(fallback, page);
 	exec_viewer("man", page);
 	die(_("no man viewer handled the request"));
 }

 static void show_info_page(const char *git_cmd)
 {
 	const char *page = cmd_to_page(git_cmd);
 	setenv("INFOPATH", system_path(GIT_INFO_PATH), 1);
 	execlp("info", "info", "gitman", page, (char *)NULL);
 	die(_("no info viewer handled the request"));
 }

 static void get_html_page_path(struct strbuf *page_path, const char *page)
 {
 	struct stat st;
 	char *to_free = NULL;

 	if (!html_path)
 		html_path = to_free = system_path(GIT_HTML_PATH);

 	/* Check that we have a git documentation directory. */
 	if (!strstr(html_path, "://")) {
 		if (stat(mkpath("%s/git.html", html_path), &st)
 		    || !S_ISREG(st.st_mode))
 			die("'%s': not a documentation directory.", html_path);
 	}

 	strbuf_init(page_path, 0);
 	strbuf_addf(page_path, "%s/%s.html", html_path, page);
 	free(to_free);
 }

 /*
  * If open_html is not defined in a platform-specific way (see for
  * example compat/mingw.h), we use the script web--browse to display
  * HTML.
  */
 #ifndef open_html
 static void open_html(const char *path)
 {
 	execl_git_cmd("web--browse", "-c", "help.browser", path, (char *)NULL);
 }
 #endif

 static void show_html_page(const char *git_cmd)
 {
 	const char *page = cmd_to_page(git_cmd);
 	struct strbuf page_path; /* it leaks but we exec bellow */

 	get_html_page_path(&page_path, page);

 	open_html(page_path.buf);
 }

 static struct {
 	const char *name;
 	const char *help;
 } common_guides[] = {
 	{ "attributes", N_("Defining attributes per path") },
 	{ "everyday", N_("Everyday Git With 20 Commands Or So") },
 	{ "glossary", N_("A Git glossary") },
 	{ "ignore", N_("Specifies intentionally untracked files to ignore") },
 	{ "modules", N_("Defining submodule properties") },
 	{ "revisions", N_("Specifying revisions and ranges for Git") },
 	{ "tutorial", N_("A tutorial introduction to Git (for version 1.5.1 or newer)") },
 	{ "workflows", N_("An overview of recommended workflows with Git") },
 };

 static void list_common_guides_help(void)
 {
 	int i, longest = 0;

 	for (i = 0; i < ARRAY_SIZE(common_guides); i++) {
 		if (longest < strlen(common_guides[i].name))
 			longest = strlen(common_guides[i].name);
 	}

 	puts(_("The common Git guides are:\n"));
 	for (i = 0; i < ARRAY_SIZE(common_guides); i++) {
 		printf("   %s   ", common_guides[i].name);
 		mput_char(' ', longest - strlen(common_guides[i].name));
 		puts(_(common_guides[i].help));
 	}
 	putchar('\n');
 }

 int cmd_help(int argc, const char **argv, const char *prefix)
 {
 	int nongit;
 	char *alias;
 	enum help_format parsed_help_format;

 	argc = parse_options(argc, argv, prefix, builtin_help_options,
 			builtin_help_usage, 0);
 	parsed_help_format = help_format;

 	if (show_all) {
 		git_config(git_help_config, NULL);
 		printf(_("usage: %s%s"), _(git_usage_string), "\n\n");
 		load_command_list("git-", &main_cmds, &other_cmds);
 		list_commands(colopts, &main_cmds, &other_cmds);
 	}

 	if (show_guides)
 		list_common_guides_help();

 	if (show_all || show_guides) {
 		printf("%s\n", _(git_more_info_string));
 		/*
 		* We're done. Ignore any remaining args
 		*/
 		return 0;
 	}

 	if (!argv[0]) {
 		printf(_("usage: %s%s"), _(git_usage_string), "\n\n");
 		list_common_cmds_help();
 		printf("\n%s\n", _(git_more_info_string));
 		return 0;
 	}

 	setup_git_directory_gently(&nongit);
 	git_config(git_help_config, NULL);

 	if (parsed_help_format != HELP_FORMAT_NONE)
 		help_format = parsed_help_format;
 	if (help_format == HELP_FORMAT_NONE)
 		help_format = parse_help_format(DEFAULT_HELP_FORMAT);

 	alias = alias_lookup(argv[0]);
 	if (alias && !is_git_command(argv[0])) {
 		printf_ln(_("`git %s' is aliased to `%s'"), argv[0], alias);
 		free(alias);
 		return 0;
 	}

 	switch (help_format) {
 	case HELP_FORMAT_NONE:
 	case HELP_FORMAT_MAN:
 		show_man_page(argv[0]);
 		break;
 	case HELP_FORMAT_INFO:
 		show_info_page(argv[0]);
 		break;
 	case HELP_FORMAT_WEB:
 		show_html_page(argv[0]);
 		break;
 	}

 	return 0;
 }
	/*
	* Builtin help command
	*/
	#include "cache.h"
	#include "builtin.h"
	#include "exec_cmd.h"
	#include "parse-options.h"
	#include "run-command.h"
	#include "column.h"
	#include "help.h"

	#ifndef DEFAULT_HELP_FORMAT
	#define DEFAULT_HELP_FORMAT "man"
	#endif

	static struct man_viewer_list {
	struct man_viewer_list *next;
	char name[FLEX_ARRAY];
	} *man_viewer_list;

	static struct man_viewer_info_list {
	struct man_viewer_info_list *next;
	const char *info;
	char name[FLEX_ARRAY];
	} *man_viewer_info_list;

	enum help_format {
	HELP_FORMAT_NONE,
	HELP_FORMAT_MAN,
	HELP_FORMAT_INFO,
	HELP_FORMAT_WEB
	};

	static const char *html_path;

	static int show_all = 0;
	static int show_guides = 0;
	static unsigned int colopts;
	static enum help_format help_format = HELP_FORMAT_NONE;
	static struct option builtin_help_options[] = {
	OPT_BOOL('a', "all", &show_all, N_("print all available commands")),
	OPT_BOOL('g', "guides", &show_guides, N_("print list of useful guides")),
	OPT_SET_INT('m', "man", &help_format, N_("show man page"), HELP_FORMAT_MAN),
	OPT_SET_INT('w', "web", &help_format, N_("show manual in web browser"),
	HELP_FORMAT_WEB),
	OPT_SET_INT('i', "info", &help_format, N_("show info page"),
	HELP_FORMAT_INFO),
	OPT_END(),
	};

	static const char * const builtin_help_usage[] = {
	N_("git help [--all] [--guides] [--man \| --web \| --info] [<command>]"),
	NULL
	};

	static enum help_format parse_help_format(const char *format)
	{
	if (!strcmp(format, "man"))
	return HELP_FORMAT_MAN;
	if (!strcmp(format, "info"))
	return HELP_FORMAT_INFO;
	if (!strcmp(format, "web") \|\| !strcmp(format, "html"))
	return HELP_FORMAT_WEB;
	die(_("unrecognized help format '%s'"), format);
	}

	static const char get_man_viewer_info(const char name)
	{
	struct man_viewer_info_list *viewer;

	for (viewer = man_viewer_info_list; viewer; viewer = viewer->next)
	{
	if (!strcasecmp(name, viewer->name))
	return viewer->info;
	}
	return NULL;
	}

	static int check_emacsclient_version(void)
	{
	struct strbuf buffer = STRBUF_INIT;
	struct child_process ec_process = CHILD_PROCESS_INIT;
	const char *argv_ec[] = { "emacsclient", "--version", NULL };
	int version;

	/* emacsclient prints its version number on stderr */
	ec_process.argv = argv_ec;
	ec_process.err = -1;
	ec_process.stdout_to_stderr = 1;
	if (start_command(&ec_process))
	return error(_("Failed to start emacsclient."));

	strbuf_read(&buffer, ec_process.err, 20);
	close(ec_process.err);

	/*
	* Don't bother checking return value, because "emacsclient --version"
	* seems to always exits with code 1.
	*/
	finish_command(&ec_process);

	if (!starts_with(buffer.buf, "emacsclient")) {
	strbuf_release(&buffer);
	return error(_("Failed to parse emacsclient version."));
	}

	strbuf_remove(&buffer, 0, strlen("emacsclient"));
	version = atoi(buffer.buf);

	if (version < 22) {
	strbuf_release(&buffer);
	return error(_("emacsclient version '%d' too old (< 22)."),
	version);
	}

	strbuf_release(&buffer);
	return 0;
	}

	static void exec_woman_emacs(const char path, const char page)
	{
	if (!check_emacsclient_version()) {
	/* This works only with emacsclient version >= 22. */
	struct strbuf man_page = STRBUF_INIT;

	if (!path)
	path = "emacsclient";
	strbuf_addf(&man_page, "(woman \"%s\")", page);
	execlp(path, "emacsclient", "-e", man_page.buf, (char *)NULL);
	warning(_("failed to exec '%s': %s"), path, strerror(errno));
	}
	}

	static void exec_man_konqueror(const char path, const char page)
	{
	const char *display = getenv("DISPLAY");
	if (display && *display) {
	struct strbuf man_page = STRBUF_INIT;
	const char *filename = "kfmclient";

	/* It's simpler to launch konqueror using kfmclient. */
	if (path) {
	const char *file = strrchr(path, '/');
	if (file && !strcmp(file + 1, "konqueror")) {
	char *new = xstrdup(path);
	char *dest = strrchr(new, '/');

	/* strlen("konqueror") == strlen("kfmclient") */
	strcpy(dest + 1, "kfmclient");
	path = new;
	}
	if (file)
	filename = file;
	} else
	path = "kfmclient";
	strbuf_addf(&man_page, "man:%s(1)", page);
	execlp(path, filename, "newTab", man_page.buf, (char *)NULL);
	warning(_("failed to exec '%s': %s"), path, strerror(errno));
	}
	}

	static void exec_man_man(const char path, const char page)
	{
	if (!path)
	path = "man";
	execlp(path, "man", page, (char *)NULL);
	warning(_("failed to exec '%s': %s"), path, strerror(errno));
	}

	static void exec_man_cmd(const char cmd, const char page)
	{
	struct strbuf shell_cmd = STRBUF_INIT;
	strbuf_addf(&shell_cmd, "%s %s", cmd, page);
	execl(SHELL_PATH, SHELL_PATH, "-c", shell_cmd.buf, (char *)NULL);
	warning(_("failed to exec '%s': %s"), cmd, strerror(errno));
	}

	static void add_man_viewer(const char *name)
	{
	struct man_viewer_list **p = &man_viewer_list;
	size_t len = strlen(name);

	while (*p)
	p = &((*p)->next);
	p = xcalloc(1, (sizeof(*p) + len + 1));
	strncpy((*p)->name, name, len);
	}

	static int supported_man_viewer(const char *name, size_t len)
	{
	return (!strncasecmp("man", name, len) \|\|
	!strncasecmp("woman", name, len) \|\|
	!strncasecmp("konqueror", name, len));
	}

	static void do_add_man_viewer_info(const char *name,
	size_t len,
	const char *value)
	{
	struct man_viewer_info_list new = xcalloc(1, sizeof(new) + len + 1);

	strncpy(new->name, name, len);
	new->info = xstrdup(value);
	new->next = man_viewer_info_list;
	man_viewer_info_list = new;
	}

	static int add_man_viewer_path(const char *name,
	size_t len,
	const char *value)
	{
	if (supported_man_viewer(name, len))
	do_add_man_viewer_info(name, len, value);
	else
	warning(_("'%s': path for unsupported man viewer.\n"
	"Please consider using 'man.<tool>.cmd' instead."),
	name);

	return 0;
	}

	static int add_man_viewer_cmd(const char *name,
	size_t len,
	const char *value)
	{
	if (supported_man_viewer(name, len))
	warning(_("'%s': cmd for supported man viewer.\n"
	"Please consider using 'man.<tool>.path' instead."),
	name);
	else
	do_add_man_viewer_info(name, len, value);

	return 0;
	}

	static int add_man_viewer_info(const char var, const char value)
	{
	const char name, subkey;
	int namelen;

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

	if (!strcmp(subkey, "path")) {
	if (!value)
	return config_error_nonbool(var);
	return add_man_viewer_path(name, namelen, value);
	}
	if (!strcmp(subkey, "cmd")) {
	if (!value)
	return config_error_nonbool(var);
	return add_man_viewer_cmd(name, namelen, value);
	}

	return 0;
	}

	static int git_help_config(const char var, const char value, void *cb)
	{
	if (starts_with(var, "column."))
	return git_column_config(var, value, "help", &colopts);
	if (!strcmp(var, "help.format")) {
	if (!value)
	return config_error_nonbool(var);
	help_format = parse_help_format(value);
	return 0;
	}
	if (!strcmp(var, "help.htmlpath")) {
	if (!value)
	return config_error_nonbool(var);
	html_path = xstrdup(value);
	return 0;
	}
	if (!strcmp(var, "man.viewer")) {
	if (!value)
	return config_error_nonbool(var);
	add_man_viewer(value);
	return 0;
	}
	if (starts_with(var, "man."))
	return add_man_viewer_info(var, value);

	return git_default_config(var, value, cb);
	}

	static struct cmdnames main_cmds, other_cmds;

	static int is_git_command(const char *s)
	{
	if (is_builtin(s))
	return 1;

	load_command_list("git-", &main_cmds, &other_cmds);
	return is_in_cmdlist(&main_cmds, s) \|\|
	is_in_cmdlist(&other_cmds, s);
	}

	static const char prepend(const char prefix, const char *cmd)
	{
	size_t pre_len = strlen(prefix);
	size_t cmd_len = strlen(cmd);
	char *p = xmalloc(pre_len + cmd_len + 1);
	memcpy(p, prefix, pre_len);
	strcpy(p + pre_len, cmd);
	return p;
	}

	static const char cmd_to_page(const char git_cmd)
	{
	if (!git_cmd)
	return "git";
	else if (starts_with(git_cmd, "git"))
	return git_cmd;
	else if (is_git_command(git_cmd))
	return prepend("git-", git_cmd);
	else
	return prepend("git", git_cmd);
	}

	static void setup_man_path(void)
	{
	struct strbuf new_path = STRBUF_INIT;
	const char *old_path = getenv("MANPATH");
	char *git_man_path = system_path(GIT_MAN_PATH);

	/* We should always put ':' after our path. If there is no
	* old_path, the ':' at the end will let 'man' to try
	* system-wide paths after ours to find the manual page. If
	* there is old_path, we need ':' as delimiter. */
	strbuf_addstr(&new_path, git_man_path);
	strbuf_addch(&new_path, ':');
	if (old_path)
	strbuf_addstr(&new_path, old_path);

	free(git_man_path);
	setenv("MANPATH", new_path.buf, 1);

	strbuf_release(&new_path);
	}

	static void exec_viewer(const char name, const char page)
	{
	const char *info = get_man_viewer_info(name);

	if (!strcasecmp(name, "man"))
	exec_man_man(info, page);
	else if (!strcasecmp(name, "woman"))
	exec_woman_emacs(info, page);
	else if (!strcasecmp(name, "konqueror"))
	exec_man_konqueror(info, page);
	else if (info)
	exec_man_cmd(info, page);
	else
	warning(_("'%s': unknown man viewer."), name);
	}

	static void show_man_page(const char *git_cmd)
	{
	struct man_viewer_list *viewer;
	const char *page = cmd_to_page(git_cmd);
	const char *fallback = getenv("GIT_MAN_VIEWER");

	setup_man_path();
	for (viewer = man_viewer_list; viewer; viewer = viewer->next)
	{
	exec_viewer(viewer->name, page); /* will return when unable */
	}
	if (fallback)
	exec_viewer(fallback, page);
	exec_viewer("man", page);
	die(_("no man viewer handled the request"));
	}

	static void show_info_page(const char *git_cmd)
	{
	const char *page = cmd_to_page(git_cmd);
	setenv("INFOPATH", system_path(GIT_INFO_PATH), 1);
	execlp("info", "info", "gitman", page, (char *)NULL);
	die(_("no info viewer handled the request"));
	}

	static void get_html_page_path(struct strbuf page_path, const char page)
	{
	struct stat st;
	char *to_free = NULL;

	if (!html_path)
	html_path = to_free = system_path(GIT_HTML_PATH);

	/* Check that we have a git documentation directory. */
	if (!strstr(html_path, "://")) {
	if (stat(mkpath("%s/git.html", html_path), &st)
	\|\| !S_ISREG(st.st_mode))
	die("'%s': not a documentation directory.", html_path);
	}

	strbuf_init(page_path, 0);
	strbuf_addf(page_path, "%s/%s.html", html_path, page);
	free(to_free);
	}

	/*
	* If open_html is not defined in a platform-specific way (see for
	* example compat/mingw.h), we use the script web--browse to display
	* HTML.
	*/
	#ifndef open_html
	static void open_html(const char *path)
	{
	execl_git_cmd("web--browse", "-c", "help.browser", path, (char *)NULL);
	}
	#endif

	static void show_html_page(const char *git_cmd)
	{
	const char *page = cmd_to_page(git_cmd);
	struct strbuf page_path; /* it leaks but we exec bellow */

	get_html_page_path(&page_path, page);

	open_html(page_path.buf);
	}

	static struct {
	const char *name;
	const char *help;
	} common_guides[] = {
	{ "attributes", N_("Defining attributes per path") },
	{ "everyday", N_("Everyday Git With 20 Commands Or So") },
	{ "glossary", N_("A Git glossary") },
	{ "ignore", N_("Specifies intentionally untracked files to ignore") },
	{ "modules", N_("Defining submodule properties") },
	{ "revisions", N_("Specifying revisions and ranges for Git") },
	{ "tutorial", N_("A tutorial introduction to Git (for version 1.5.1 or newer)") },
	{ "workflows", N_("An overview of recommended workflows with Git") },
	};

	static void list_common_guides_help(void)
	{
	int i, longest = 0;

	for (i = 0; i < ARRAY_SIZE(common_guides); i++) {
	if (longest < strlen(common_guides[i].name))
	longest = strlen(common_guides[i].name);
	}

	puts(_("The common Git guides are:\n"));
	for (i = 0; i < ARRAY_SIZE(common_guides); i++) {
	printf(" %s ", common_guides[i].name);
	mput_char(' ', longest - strlen(common_guides[i].name));
	puts(_(common_guides[i].help));
	}
	putchar('\n');
	}

	int cmd_help(int argc, const char *argv, const char prefix)
	{
	int nongit;
	char *alias;
	enum help_format parsed_help_format;

	argc = parse_options(argc, argv, prefix, builtin_help_options,
	builtin_help_usage, 0);
	parsed_help_format = help_format;

	if (show_all) {
	git_config(git_help_config, NULL);
	printf(_("usage: %s%s"), _(git_usage_string), "\n\n");
	load_command_list("git-", &main_cmds, &other_cmds);
	list_commands(colopts, &main_cmds, &other_cmds);
	}

	if (show_guides)
	list_common_guides_help();

	if (show_all \|\| show_guides) {
	printf("%s\n", _(git_more_info_string));
	/*
	* We're done. Ignore any remaining args
	*/
	return 0;
	}

	if (!argv[0]) {
	printf(_("usage: %s%s"), _(git_usage_string), "\n\n");
	list_common_cmds_help();
	printf("\n%s\n", _(git_more_info_string));
	return 0;
	}

	setup_git_directory_gently(&nongit);
	git_config(git_help_config, NULL);

	if (parsed_help_format != HELP_FORMAT_NONE)
	help_format = parsed_help_format;
	if (help_format == HELP_FORMAT_NONE)
	help_format = parse_help_format(DEFAULT_HELP_FORMAT);

	alias = alias_lookup(argv[0]);
	if (alias && !is_git_command(argv[0])) {
	printf_ln(_("`git %s' is aliased to `%s'"), argv[0], alias);
	free(alias);
	return 0;
	}

	switch (help_format) {
	case HELP_FORMAT_NONE:
	case HELP_FORMAT_MAN:
	show_man_page(argv[0]);
	break;
	case HELP_FORMAT_INFO:
	show_info_page(argv[0]);
	break;
	case HELP_FORMAT_WEB:
	show_html_page(argv[0]);
	break;
	}

	return 0;
	}