1 files changed, 459 insertions, 87 deletions
diff --git a/help.c b/help.c
index 1dfa0b0582..973e47cdc3 100644
--- a/help.c
+++ b/help.c
@@ -1,20 +1,142 @@
 #include "cache.h"
+#include "config.h"
 #include "builtin.h"
-#include "exec_cmd.h"
+#include "exec-cmd.h"
+#include "run-command.h"
 #include "levenshtein.h"
 #include "help.h"
-#include "common-cmds.h"
+#include "command-list.h"
 #include "string-list.h"
 #include "column.h"
 #include "version.h"
+#include "refs.h"
+#include "parse-options.h"
+#include "prompt.h"
+
+struct category_description {
+	uint32_t category;
+	const char *desc;
+};
+static uint32_t common_mask =
+	CAT_init | CAT_worktree | CAT_info |
+	CAT_history | CAT_remote;
+static struct category_description common_categories[] = {
+	{ CAT_init, N_("start a working area (see also: git help tutorial)") },
+	{ CAT_worktree, N_("work on the current change (see also: git help everyday)") },
+	{ CAT_info, N_("examine the history and state (see also: git help revisions)") },
+	{ CAT_history, N_("grow, mark and tweak your common history") },
+	{ CAT_remote, N_("collaborate (see also: git help workflows)") },
+	{ 0, NULL }
+};
+static struct category_description main_categories[] = {
+	{ CAT_mainporcelain, N_("Main Porcelain Commands") },
+	{ CAT_ancillarymanipulators, N_("Ancillary Commands / Manipulators") },
+	{ CAT_ancillaryinterrogators, N_("Ancillary Commands / Interrogators") },
+	{ CAT_foreignscminterface, N_("Interacting with Others") },
+	{ CAT_plumbingmanipulators, N_("Low-level Commands / Manipulators") },
+	{ CAT_plumbinginterrogators, N_("Low-level Commands / Interrogators") },
+	{ CAT_synchingrepositories, N_("Low-level Commands / Syncing Repositories") },
+	{ CAT_purehelpers, N_("Low-level Commands / Internal Helpers") },
+	{ 0, NULL }
+};
+
+static const char *drop_prefix(const char *name, uint32_t category)
+{
+	const char *new_name;
 
-void add_cmdname(struct cmdnames *cmds, const char *name, int len)
+	if (skip_prefix(name, "git-", &new_name))
+		return new_name;
+	if (category == CAT_guide && skip_prefix(name, "git", &new_name))
+		return new_name;
+	return name;
+
+}
+
+static void extract_cmds(struct cmdname_help **p_cmds, uint32_t mask)
 {
-	struct cmdname *ent = xmalloc(sizeof(*ent) + len + 1);
+	int i, nr = 0;
+	struct cmdname_help *cmds;
+
+	if (ARRAY_SIZE(command_list) == 0)
+		BUG("empty command_list[] is a sign of broken generate-cmdlist.sh");
+
+	ALLOC_ARRAY(cmds, ARRAY_SIZE(command_list) + 1);
+
+	for (i = 0; i < ARRAY_SIZE(command_list); i++) {
+		const struct cmdname_help *cmd = command_list + i;
+
+		if (!(cmd->category & mask))
+			continue;
 
+		cmds[nr] = *cmd;
+		cmds[nr].name = drop_prefix(cmd->name, cmd->category);
+
+		nr++;
+	}
+	cmds[nr].name = NULL;
+	*p_cmds = cmds;
+}
+
+static void print_command_list(const struct cmdname_help *cmds,
+			       uint32_t mask, int longest)
+{
+	int i;
+
+	for (i = 0; cmds[i].name; i++) {
+		if (cmds[i].category & mask) {
+			size_t len = strlen(cmds[i].name);
+			printf("   %s   ", cmds[i].name);
+			if (longest > len)
+				mput_char(' ', longest - len);
+			puts(_(cmds[i].help));
+		}
+	}
+}
+
+static int cmd_name_cmp(const void *elem1, const void *elem2)
+{
+	const struct cmdname_help *e1 = elem1;
+	const struct cmdname_help *e2 = elem2;
+
+	return strcmp(e1->name, e2->name);
+}
+
+static void print_cmd_by_category(const struct category_description *catdesc,
+				  int *longest_p)
+{
+	struct cmdname_help *cmds;
+	int longest = 0;
+	int i, nr = 0;
+	uint32_t mask = 0;
+
+	for (i = 0; catdesc[i].desc; i++)
+		mask |= catdesc[i].category;
+
+	extract_cmds(&cmds, mask);
+
+	for (i = 0; cmds[i].name; i++, nr++) {
+		if (longest < strlen(cmds[i].name))
+			longest = strlen(cmds[i].name);
+	}
+	QSORT(cmds, nr, cmd_name_cmp);
+
+	for (i = 0; catdesc[i].desc; i++) {
+		uint32_t mask = catdesc[i].category;
+		const char *desc = catdesc[i].desc;
+
+		printf("\n%s\n", _(desc));
+		print_command_list(cmds, mask, longest);
+	}
+	free(cmds);
+	if (longest_p)
+		*longest_p = longest;
+}
+
+void add_cmdname(struct cmdnames *cmds, const char *name, int len)
+{
+	struct cmdname *ent;
+	FLEX_ALLOC_MEM(ent, name, name, len);
 	ent->len = len;
-	memcpy(ent->name, name, len);
-	ent->name[len] = 0;
 
 	ALLOC_GROW(cmds->names, cmds->cnt + 1, cmds->alloc);
 	cmds->names[cmds->cnt++] = ent;
@@ -77,8 +199,7 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
 	cmds->cnt = cj;
 }
 
-static void pretty_print_string_list(struct cmdnames *cmds,
-				     unsigned int colopts)
+static void pretty_print_cmdnames(struct cmdnames *cmds, unsigned int colopts)
 {
 	struct string_list list = STRING_LIST_INIT_NODUP;
 	struct column_options copts;
@@ -98,41 +219,10 @@ static void pretty_print_string_list(struct cmdnames *cmds,
 	string_list_clear(&list, 0);
 }
 
-static int is_executable(const char *name)
-{
-	struct stat st;
-
-	if (stat(name, &st) || /* stat, not lstat */
-	    !S_ISREG(st.st_mode))
-		return 0;
-
-#if defined(WIN32) || defined(__CYGWIN__)
-#if defined(__CYGWIN__)
-if ((st.st_mode & S_IXUSR) == 0)
-#endif
-{	/* cannot trust the executable bit, peek into the file instead */
-	char buf[3] = { 0 };
-	int n;
-	int fd = open(name, O_RDONLY);
-	st.st_mode &= ~S_IXUSR;
-	if (fd >= 0) {
-		n = read(fd, buf, 2);
-		if (n == 2)
-			/* DOS executables start with "MZ" */
-			if (!strcmp(buf, "#!") || !strcmp(buf, "MZ"))
-				st.st_mode |= S_IXUSR;
-		close(fd);
-	}
-}
-#endif
-	return st.st_mode & S_IXUSR;
-}
-
 static void list_commands_in_dir(struct cmdnames *cmds,
 					 const char *path,
 					 const char *prefix)
 {
-	int prefix_len;
 	DIR *dir = opendir(path);
 	struct dirent *de;
 	struct strbuf buf = STRBUF_INIT;
@@ -142,15 +232,15 @@ static void list_commands_in_dir(struct cmdnames *cmds,
 		return;
 	if (!prefix)
 		prefix = "git-";
-	prefix_len = strlen(prefix);
 
 	strbuf_addf(&buf, "%s/", path);
 	len = buf.len;
 
 	while ((de = readdir(dir)) != NULL) {
-		int entlen;
+		const char *ent;
+		size_t entlen;
 
-		if (prefixcmp(de->d_name, prefix))
+		if (!skip_prefix(de->d_name, prefix, &ent))
 			continue;
 
 		strbuf_setlen(&buf, len);
@@ -158,11 +248,10 @@ static void list_commands_in_dir(struct cmdnames *cmds,
 		if (!is_executable(buf.buf))
 			continue;
 
-		entlen = strlen(de->d_name) - prefix_len;
-		if (has_extension(de->d_name, ".exe"))
-			entlen -= 4;
+		entlen = strlen(ent);
+		strip_suffix(ent, ".exe", &entlen);
 
-		add_cmdname(cmds, de->d_name + prefix_len, entlen);
+		add_cmdname(cmds, ent, entlen);
 	}
 	closedir(dir);
 	strbuf_release(&buf);
@@ -175,10 +264,11 @@ void load_command_list(const char *prefix,
 	const char *env_path = getenv("PATH");
 	const char *exec_path = git_exec_path();
 
+	load_builtin_commands(prefix, main_cmds);
+
 	if (exec_path) {
 		list_commands_in_dir(main_cmds, exec_path, prefix);
-		qsort(main_cmds->names, main_cmds->cnt,
-		      sizeof(*main_cmds->names), cmdname_compare);
+		QSORT(main_cmds->names, main_cmds->cnt, cmdname_compare);
 		uniq(main_cmds);
 	}
 
@@ -197,49 +287,192 @@ void load_command_list(const char *prefix,
 		}
 		free(paths);
 
-		qsort(other_cmds->names, other_cmds->cnt,
-		      sizeof(*other_cmds->names), cmdname_compare);
+		QSORT(other_cmds->names, other_cmds->cnt, cmdname_compare);
 		uniq(other_cmds);
 	}
 	exclude_cmds(other_cmds, main_cmds);
 }
 
-void list_commands(unsigned int colopts,
-		   struct cmdnames *main_cmds, struct cmdnames *other_cmds)
+static int get_colopts(const char *var, const char *value, void *data)
 {
+	unsigned int *colopts = data;
+
+	if (starts_with(var, "column."))
+		return git_column_config(var, value, "help", colopts);
+
+	return 0;
+}
+
+void list_commands(struct cmdnames *main_cmds, struct cmdnames *other_cmds)
+{
+	unsigned int colopts = 0;
+	git_config(get_colopts, &colopts);
+
 	if (main_cmds->cnt) {
 		const char *exec_path = git_exec_path();
 		printf_ln(_("available git commands in '%s'"), exec_path);
 		putchar('\n');
-		pretty_print_string_list(main_cmds, colopts);
+		pretty_print_cmdnames(main_cmds, colopts);
 		putchar('\n');
 	}
 
 	if (other_cmds->cnt) {
 		printf_ln(_("git commands available from elsewhere on your $PATH"));
 		putchar('\n');
-		pretty_print_string_list(other_cmds, colopts);
+		pretty_print_cmdnames(other_cmds, colopts);
 		putchar('\n');
 	}
 }
 
 void list_common_cmds_help(void)
 {
-	int i, longest = 0;
+	puts(_("These are common Git commands used in various situations:"));
+	print_cmd_by_category(common_categories, NULL);
+}
+
+void list_all_main_cmds(struct string_list *list)
+{
+	struct cmdnames main_cmds, other_cmds;
+	int i;
+
+	memset(&main_cmds, 0, sizeof(main_cmds));
+	memset(&other_cmds, 0, sizeof(other_cmds));
+	load_command_list("git-", &main_cmds, &other_cmds);
+
+	for (i = 0; i < main_cmds.cnt; i++)
+		string_list_append(list, main_cmds.names[i]->name);
+
+	clean_cmdnames(&main_cmds);
+	clean_cmdnames(&other_cmds);
+}
+
+void list_all_other_cmds(struct string_list *list)
+{
+	struct cmdnames main_cmds, other_cmds;
+	int i;
+
+	memset(&main_cmds, 0, sizeof(main_cmds));
+	memset(&other_cmds, 0, sizeof(other_cmds));
+	load_command_list("git-", &main_cmds, &other_cmds);
+
+	for (i = 0; i < other_cmds.cnt; i++)
+		string_list_append(list, other_cmds.names[i]->name);
+
+	clean_cmdnames(&main_cmds);
+	clean_cmdnames(&other_cmds);
+}
+
+void list_cmds_by_category(struct string_list *list,
+			   const char *cat)
+{
+	int i, n = ARRAY_SIZE(command_list);
+	uint32_t cat_id = 0;
 
-	for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
-		if (longest < strlen(common_cmds[i].name))
-			longest = strlen(common_cmds[i].name);
+	for (i = 0; category_names[i]; i++) {
+		if (!strcmp(cat, category_names[i])) {
+			cat_id = 1UL << i;
+			break;
+		}
 	}
+	if (!cat_id)
+		die(_("unsupported command listing type '%s'"), cat);
+
+	for (i = 0; i < n; i++) {
+		struct cmdname_help *cmd = command_list + i;
 
-	puts(_("The most commonly used git commands are:"));
-	for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
-		printf("   %s   ", common_cmds[i].name);
-		mput_char(' ', longest - strlen(common_cmds[i].name));
-		puts(_(common_cmds[i].help));
+		if (!(cmd->category & cat_id))
+			continue;
+		string_list_append(list, drop_prefix(cmd->name, cmd->category));
 	}
 }
 
+void list_cmds_by_config(struct string_list *list)
+{
+	const char *cmd_list;
+
+	if (git_config_get_string_tmp("completion.commands", &cmd_list))
+		return;
+
+	string_list_sort(list);
+	string_list_remove_duplicates(list, 0);
+
+	while (*cmd_list) {
+		struct strbuf sb = STRBUF_INIT;
+		const char *p = strchrnul(cmd_list, ' ');
+
+		strbuf_add(&sb, cmd_list, p - cmd_list);
+		if (sb.buf[0] == '-')
+			string_list_remove(list, sb.buf + 1, 0);
+		else
+			string_list_insert(list, sb.buf);
+		strbuf_release(&sb);
+		while (*p == ' ')
+			p++;
+		cmd_list = p;
+	}
+}
+
+void list_guides_help(void)
+{
+	struct category_description catdesc[] = {
+		{ CAT_guide, N_("The Git concept guides are:") },
+		{ 0, NULL }
+	};
+	print_cmd_by_category(catdesc, NULL);
+	putchar('\n');
+}
+
+static int get_alias(const char *var, const char *value, void *data)
+{
+	struct string_list *list = data;
+
+	if (skip_prefix(var, "alias.", &var))
+		string_list_append(list, var)->util = xstrdup(value);
+
+	return 0;
+}
+
+void list_all_cmds_help(void)
+{
+	struct string_list others = STRING_LIST_INIT_DUP;
+	struct string_list alias_list = STRING_LIST_INIT_DUP;
+	struct cmdname_help *aliases;
+	int i, longest;
+
+	printf_ln(_("See 'git help <command>' to read about a specific subcommand"));
+	print_cmd_by_category(main_categories, &longest);
+
+	list_all_other_cmds(&others);
+	if (others.nr)
+		printf("\n%s\n", _("External commands"));
+	for (i = 0; i < others.nr; i++)
+		printf("   %s\n", others.items[i].string);
+	string_list_clear(&others, 0);
+
+	git_config(get_alias, &alias_list);
+	string_list_sort(&alias_list);
+
+	for (i = 0; i < alias_list.nr; i++) {
+		size_t len = strlen(alias_list.items[i].string);
+		if (longest < len)
+			longest = len;
+	}
+
+	if (alias_list.nr) {
+		printf("\n%s\n", _("Command aliases"));
+		ALLOC_ARRAY(aliases, alias_list.nr + 1);
+		for (i = 0; i < alias_list.nr; i++) {
+			aliases[i].name = alias_list.items[i].string;
+			aliases[i].help = alias_list.items[i].util;
+			aliases[i].category = 1;
+		}
+		aliases[alias_list.nr].name = NULL;
+		print_command_list(aliases, 1, longest);
+		free(aliases);
+	}
+	string_list_clear(&alias_list, 1);
+}
+
 int is_in_cmdlist(struct cmdnames *c, const char *s)
 {
 	int i;
@@ -252,13 +485,32 @@ int is_in_cmdlist(struct cmdnames *c, const char *s)
 static int autocorrect;
 static struct cmdnames aliases;
 
+#define AUTOCORRECT_PROMPT (-3)
+#define AUTOCORRECT_NEVER (-2)
+#define AUTOCORRECT_IMMEDIATELY (-1)
+
 static int git_unknown_cmd_config(const char *var, const char *value, void *cb)
 {
-	if (!strcmp(var, "help.autocorrect"))
-		autocorrect = git_config_int(var,value);
+	const char *p;
+
+	if (!strcmp(var, "help.autocorrect")) {
+		if (!value)
+			return config_error_nonbool(var);
+		if (!strcmp(value, "never")) {
+			autocorrect = AUTOCORRECT_NEVER;
+		} else if (!strcmp(value, "immediate")) {
+			autocorrect = AUTOCORRECT_IMMEDIATELY;
+		} else if (!strcmp(value, "prompt")) {
+			autocorrect = AUTOCORRECT_PROMPT;
+		} else {
+			int v = git_config_int(var, value);
+			autocorrect = (v < 0)
+				? AUTOCORRECT_IMMEDIATELY : v;
+		}
+	}
 	/* Also use aliases for command lookup */
-	if (!prefixcmp(var, "alias."))
-		add_cmdname(&aliases, var + 6, strlen(var + 6));
+	if (skip_prefix(var, "alias.", &p))
+		add_cmdname(&aliases, p, strlen(p));
 
 	return git_default_config(var, value, cb);
 }
@@ -279,9 +531,8 @@ static void add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
 
 	for (i = 0; i < old->cnt; i++)
 		cmds->names[cmds->cnt++] = old->names[i];
-	free(old->names);
+	FREE_AND_NULL(old->names);
 	old->cnt = 0;
-	old->names = NULL;
 }
 
 /* An empirically derived magic number */
@@ -296,21 +547,34 @@ const char *help_unknown_cmd(const char *cmd)
 {
 	int i, n, best_similarity = 0;
 	struct cmdnames main_cmds, other_cmds;
+	struct cmdname_help *common_cmds;
 
 	memset(&main_cmds, 0, sizeof(main_cmds));
 	memset(&other_cmds, 0, sizeof(other_cmds));
 	memset(&aliases, 0, sizeof(aliases));
 
-	git_config(git_unknown_cmd_config, NULL);
+	read_early_config(git_unknown_cmd_config, NULL);
+
+	/*
+	 * Disable autocorrection prompt in a non-interactive session
+	 */
+	if ((autocorrect == AUTOCORRECT_PROMPT) && (!isatty(0) || !isatty(2)))
+		autocorrect = AUTOCORRECT_NEVER;
+
+	if (autocorrect == AUTOCORRECT_NEVER) {
+		fprintf_ln(stderr, _("git: '%s' is not a git command. See 'git --help'."), cmd);
+		exit(1);
+	}
 
 	load_command_list("git-", &main_cmds, &other_cmds);
 
 	add_cmd_list(&main_cmds, &aliases);
 	add_cmd_list(&main_cmds, &other_cmds);
-	qsort(main_cmds.names, main_cmds.cnt,
-	      sizeof(main_cmds.names), cmdname_compare);
+	QSORT(main_cmds.names, main_cmds.cnt, cmdname_compare);
 	uniq(&main_cmds);
 
+	extract_cmds(&common_cmds, common_mask);
+
 	/* This abuses cmdname->len for levenshtein distance */
 	for (i = 0, n = 0; i < main_cmds.cnt; i++) {
 		int cmp = 0; /* avoid compiler stupidity */
@@ -325,13 +589,13 @@ const char *help_unknown_cmd(const char *cmd)
 			die(_(bad_interpreter_advice), cmd, cmd);
 
 		/* Does the candidate appear in common_cmds list? */
-		while (n < ARRAY_SIZE(common_cmds) &&
+		while (common_cmds[n].name &&
 		       (cmp = strcmp(common_cmds[n].name, candidate)) < 0)
 			n++;
-		if ((n < ARRAY_SIZE(common_cmds)) && !cmp) {
+		if (common_cmds[n].name && !cmp) {
 			/* Yes, this is one of the common commands */
 			n++; /* use the entry from common_cmds[] */
-			if (!prefixcmp(candidate, cmd)) {
+			if (starts_with(candidate, cmd)) {
 				/* Give prefix match a very good score */
 				main_cmds.names[i]->len = 0;
 				continue;
@@ -341,9 +605,9 @@ const char *help_unknown_cmd(const char *cmd)
 		main_cmds.names[i]->len =
 			levenshtein(cmd, candidate, 0, 2, 1, 3) + 1;
 	}
+	FREE_AND_NULL(common_cmds);
 
-	qsort(main_cmds.names, main_cmds.cnt,
-	      sizeof(*main_cmds.names), levenshtein_compare);
+	QSORT(main_cmds.names, main_cmds.cnt, levenshtein_compare);
 
 	if (!main_cmds.cnt)
 		die(_("Uh oh. Your system reports no Git commands at all."));
@@ -369,13 +633,28 @@ const char *help_unknown_cmd(const char *cmd)
 		clean_cmdnames(&main_cmds);
 		fprintf_ln(stderr,
 			   _("WARNING: You called a Git command named '%s', "
-			     "which does not exist.\n"
-			     "Continuing under the assumption that you meant '%s'"),
-			cmd, assumed);
-		if (autocorrect > 0) {
-			fprintf_ln(stderr, _("in %0.1f seconds automatically..."),
-				(float)autocorrect/10.0);
-			poll(NULL, 0, autocorrect * 100);
+			     "which does not exist."),
+			   cmd);
+		if (autocorrect == AUTOCORRECT_IMMEDIATELY)
+			fprintf_ln(stderr,
+				   _("Continuing under the assumption that "
+				     "you meant '%s'."),
+				   assumed);
+		else if (autocorrect == AUTOCORRECT_PROMPT) {
+			char *answer;
+			struct strbuf msg = STRBUF_INIT;
+			strbuf_addf(&msg, _("Run '%s' instead? (y/N)"), assumed);
+			answer = git_prompt(msg.buf, PROMPT_ECHO);
+			strbuf_release(&msg);
+			if (!(starts_with(answer, "y") ||
+			      starts_with(answer, "Y")))
+				exit(1);
+		} else {
+			fprintf_ln(stderr,
+				   _("Continuing in %0.1f seconds, "
+				     "assuming that you meant '%s'."),
+				   (float)autocorrect/10.0, assumed);
+			sleep_millisec(autocorrect * 100);
 		}
 		return assumed;
 	}
@@ -384,8 +663,8 @@ const char *help_unknown_cmd(const char *cmd)
 
 	if (SIMILAR_ENOUGH(best_similarity)) {
 		fprintf_ln(stderr,
-			   Q_("\nDid you mean this?",
-			      "\nDid you mean one of these?",
+			   Q_("\nThe most similar command is",
+			      "\nThe most similar commands are",
 			   n));
 
 		for (i = 0; i < n; i++)
@@ -395,8 +674,101 @@ const char *help_unknown_cmd(const char *cmd)
 	exit(1);
 }
 
+void get_version_info(struct strbuf *buf, int show_build_options)
+{
+	/*
+	 * The format of this string should be kept stable for compatibility
+	 * with external projects that rely on the output of "git version".
+	 *
+	 * Always show the version, even if other options are given.
+	 */
+	strbuf_addf(buf, "git version %s\n", git_version_string);
+
+	if (show_build_options) {
+		strbuf_addf(buf, "cpu: %s\n", GIT_HOST_CPU);
+		if (git_built_from_commit_string[0])
+			strbuf_addf(buf, "built from commit: %s\n",
+			       git_built_from_commit_string);
+		else
+			strbuf_addstr(buf, "no commit associated with this build\n");
+		strbuf_addf(buf, "sizeof-long: %d\n", (int)sizeof(long));
+		strbuf_addf(buf, "sizeof-size_t: %d\n", (int)sizeof(size_t));
+		strbuf_addf(buf, "shell-path: %s\n", SHELL_PATH);
+		/* NEEDSWORK: also save and output GIT-BUILD_OPTIONS? */
+	}
+}
+
 int cmd_version(int argc, const char **argv, const char *prefix)
 {
-	printf("git version %s\n", git_version_string);
+	struct strbuf buf = STRBUF_INIT;
+	int build_options = 0;
+	const char * const usage[] = {
+		N_("git version [<options>]"),
+		NULL
+	};
+	struct option options[] = {
+		OPT_BOOL(0, "build-options", &build_options,
+			 "also print build options"),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options, usage, 0);
+
+	get_version_info(&buf, build_options);
+	printf("%s", buf.buf);
+
+	strbuf_release(&buf);
+
+	return 0;
+}
+
+struct similar_ref_cb {
+	const char *base_ref;
+	struct string_list *similar_refs;
+};
+
+static int append_similar_ref(const char *refname, const struct object_id *oid,
+			      int flags, void *cb_data)
+{
+	struct similar_ref_cb *cb = (struct similar_ref_cb *)(cb_data);
+	char *branch = strrchr(refname, '/') + 1;
+
+	/* A remote branch of the same name is deemed similar */
+	if (starts_with(refname, "refs/remotes/") &&
+	    !strcmp(branch, cb->base_ref))
+		string_list_append_nodup(cb->similar_refs,
+					 shorten_unambiguous_ref(refname, 1));
 	return 0;
 }
+
+static struct string_list guess_refs(const char *ref)
+{
+	struct similar_ref_cb ref_cb;
+	struct string_list similar_refs = STRING_LIST_INIT_DUP;
+
+	ref_cb.base_ref = ref;
+	ref_cb.similar_refs = &similar_refs;
+	for_each_ref(append_similar_ref, &ref_cb);
+	return similar_refs;
+}
+
+NORETURN void help_unknown_ref(const char *ref, const char *cmd,
+			       const char *error)
+{
+	int i;
+	struct string_list suggested_refs = guess_refs(ref);
+
+	fprintf_ln(stderr, _("%s: %s - %s"), cmd, ref, error);
+
+	if (suggested_refs.nr > 0) {
+		fprintf_ln(stderr,
+			   Q_("\nDid you mean this?",
+			      "\nDid you mean one of these?",
+			      suggested_refs.nr));
+		for (i = 0; i < suggested_refs.nr; i++)
+			fprintf(stderr, "\t%s\n", suggested_refs.items[i].string);
+	}
+
+	string_list_clear(&suggested_refs, 0);
+	exit(1);
+}